C. M. Child

Physiological dominance and physiological isolation in development and reconstitution

The mature organism is obviously not a predetermined harmony of independent parts. I t is a well known fact that physiological relations of various sorts exist between its organs and parts, that is, one organ or part influences another ill some way. These physiological relations become exceedingly complex in the higher animals and man, but in general fall into two groups, the transmissive or dynanfic and the transportative or material relations. The transmissive relations consist in thc transmission of energy without the mass transporation of substance. Any form of energy may be transmitted under the proper conditions in protoplasm, but the most important form of transmissive relation is the transmission of the physiological process commonly known as excitation, which finds its most advanced development in nervous conduction in thc higher animals and man. The transportative relations consist in the for. mation of a certain substance in a certain organ or organs and its transportation in mass to par~s whose condition or activities it infhlences in some way. These relations find their highest development in the endocrine substances, the so.called hormones, inhibiting substances etc. produced in certain organs and transported to and affecting others, but they also include the transport of oxygen, carbon dioxide and other metabolic products. The general term, physiological correlation is often used to inchlde all physiological relations between parts, both transmissive and transportative, but when we analyse physiological correlation we find that it consists of relations of control and being controlled, of physiological dominance and subordination. In transmissive relations, for example

The Head Frequency Gradient in Euplanaria dorotocephala

VARIOUS lines of evidence indicate that in Euplanaria (Planaria) dorotocephala and certain other planarian species V which undergo fission at a more or less definite post-oral level the bodies of the larger animals represent two or more zooids, which are physiologically-perhaps histologically to some extentbut not morphologically distinguishable (Child, I910, 191 IC, 1913, 1930). The anterior zooid includes the head and the body anterior to the level of fission which is a short distance posterior to the mouth but varies somewhat in position in different individuals and species. The body posterior to this level shows evidences of the presence of one or more zooids according to length, and a posterior growing region. Data given in earlier papers show that form and structure of the reconstituted planarian head and the frequency of development of a head differ in certain species with length of piece and level of body at which reconstitution occurs (Child, 19I a, 1912, 1916a; Behre, 1918; Buchanan, 1922; Sivickis, 1923; Abeloos, 1930). The various head-forms constitute a graded series representing different degrees of differential inhibition of head development, with the normal head at one extreme and the acephalic form at the other (Child, 19g1Ia, I92I). For convenience the various members

Physiological isolation of parts and fission in planaria

The occurrence of fission in various species of Planaria has long been known; the peculiar method of fission by rupture of the tissues in a more or less sharply defined region of the body without any preceding visible differentiation of a second zooid, is in strong contrast to the method of asexual reproduction in the rhabdocoel, where the first visible phenomena are the differentiation of parts of .the new individual, and separation occurs only after differentiation is practically complete. The present paper is chiefly concerned with certain experiments which have demonstrated the possibility of controlling experimentally the occurrence of fission in Planaria dorotocephala Woodworth, without relation to nutrition. The results of these experiments are significant, not only for Planaria but for various processes of reproduction in various organisms.

An analysis of form-regulation in Tubularia

Summary1)In the metamorphosis of the primordium into the hydranth a change in length occurs. In oral hydranths from the extreme distal end of the stem the length is 35% less than that of the primordium. The reduction in length is less in aboral than in oral structures from the same level and decreases in both oral and aboral structures with increasing distance from the distal end, until in aboral structures from the extreme proximal ends of long stems the length of the hydranth may be greater than that of the primordium instead of less.2)These changes of length between primordium and hydranth show regional and polar differences parallel to the differences in size of the hydranth and are due chiefly to the fact that hydranths of very different size arise from primordia which develop within a cylinder, the perisarc, which differs only slightly in diameter in different regions.3)The proportions of the hydranths after emergence differ with polar differences in position and probably also to some extent with regional differences in position. These differences in proportion of the hydranths are not parallel to the regional and polar differences in proportions of the primordia but are in part in the reverse direction.4)The absence of parallelism in the regional and polar differences in proportion of primordia and hydranths is due to the fact that the two are different functional systems and that the factors determining the proportions differ at least quantitatively in the two systems.Zusammenfassung1)Bei der Verwandlung des Primordiums in die Hydrante tritt eine Längenänderung auf. Bei oralen Hydranten vom äußersten distalen Stammende beträgt die Länge 35% weniger als die des Primordiums. Die Längenreduction ist bei aboralen Bildungen geringer als bei oralen aus demselben Niveau und nimmt bei beiden, oralen und aboralen Bildungen, mit der wachsenden Entfernung vom distalen Ende ab, bis schließlich bei aboralen Strukturen von den äußersten proximalen Enden langer Stämme die Hydrantenlänge möglicherweise größer ist als die des Primordiums, anstatt geringer.2)Diese Längenänderungen zwischen Primordium und Hydrante zeigen regionäre und polare Unterschiede parallel mit den Verschiedenheiten der Hydrantengröße und beruhen wesentlich auf dem Umstand, daß Hydranten sehr verschiedener Größe von Primordien sich erheben, welche sich im Bereiche eines Perisarkcylinders entwickeln, der in verschiedenen Bezirken nur unbedeutende Durchmesserunterschiede zeigt.3)Die Proportionen der Hydranten nach ihrem Auftauchen unterscheiden sich durch polare Verschiedenheiten und wahrscheinlich auch in gewissem Grade durch regionäre Verschiedenheiten in ihrer Stellung. Diese Proportionsunterschiede der Hydranten gehen den entsprechenden der Primordia nicht parallel, sondern verlaufen zum Teil in umgekehrter Richtung.4)Das Fehlen der Übereinstimmung in den regionären und polaren Proportionsunterschieden bei Primordien und Hydranten beruht auf dem Umstand, daß die beiden verschiedene funktionelle Systeme darstellen, und daß die die Proportionen bestimmenden Faktoren mindestens quantitativ bei den beiden Systemen verschieden sind.

Studies on regulation

Summary1)Form-regulation (morphallaxis) in pieces and zooids of Stenostoma, which have been separated from individuals or chains, can be controlled experimentally to a large extent, by preventing the pieces or zooids from coming into contact with surfaces and moving over them.2)Form-regulation is not the reaction of the tissues to stimuli connected with contact, but is due to the tension exerted on the plastic tissues of Stenostoma by the movements of the animal (piece or zooid).3)The principal factor in the production of the change of form is the longitudinal tension caused by the use of the ventral surface, especially at the posterior end, as an organ of attachment, while the cilia of the lateral and dorsal regions continue to beat. The peristaltic contractions exert a certain amount of pressure on the intestinal contents, and so indirectly upon the body-wall, which probably also tends to cause elongation of the body. The reversed movement of the cilia of the ventral band may also cause some degree of tension in the ventral region and so aid in the elongation and change of form.4)The development of the tail in Stenostoma is primarily the direct result of mechanical conditions. Its formation can be inhibited, delayed or accelerated by altering experimentally the tension to which this region of the body is subjected, i. e., by preventing the zooid or piece from coming into contact with surfaces and creeping over them, or by permitting such contact in greater or less degree.5)The form of the tail in its earlier stages is dependent upon the particular mechanical conditions to which the posterior region of the piece or zooid has heen subjected.Zusammenfassung1)Bei Stücken und Zooïden von Stenostoma, welche voa Individuen der Ketten getrennt wurden, kann die Formregulation (Morphallaxis) zum großen Theil experimentell kontrollirt werden, indem man die Stücke oder Zooïde verhindert, mit Oberflächen in Berührung zu kommen oder sich über dieselben hin zu bewegen.2)Die Formregulation ist nicht die Reaktion der Gewebe auf Kontaktreize, sondern ist das Ergebnis der durch die Bewegungen des Thieres, Stücks oder Zooïds auf die plastischen Gewebe ausgeübten Zugspannung.3)Der hauptsächlichste Faktor bei der Erzeugung der Formveränderung ist die Längsspannung. welche die Benutzung der Bauchfläche, speciell ihres Hinterendes, als Haftorgan verursacht, während die Wimpern der Rücken- und Seitenregion zu schlagen fortfahren. Die peristaltischen Kontraktionen üben einen gewissen Druck auf den Darminhalt und damit indirekt auf die Körperwand aus, wodurch wahrscheinlich eine weitere Tendenz zur Körperverlängerung entsteht. Die umgekehrte Bewegungsrichtung der Wimpern des Bauchstreifens mag gleichfalls einen gewissen Grad von Spannung in der Bauchgegend verursachen und somit die Verlängerung und Formveränderung begünstigen.4)Die Entwickelung des Schwanzes von Stenostoma ist primär das direkte Ergebnis mechanischer Bedingungen. Seine Bildung kann verhindert, verzögert und beschleunigt werden, indem man experimentell die Spannungsverhältnisse dieser Körpergegend ändert, nämlich das Stück oder Zooïd an der Berührung einer Fläche oder an dem Kriechen über eine Fläche verhindert, oder aber solche Berührung in geringem oder größerem Maße zulässt.5)Die Form des Schwanzes in ihren früheren Entwickelungsstadien hängt von den speciellen mechanischen Bedingungen ab, denen der hintere Bezirk des Stücks oder Zooïds unterworfen war.

Contributions toward a theory of regulation

SummaryA complete and consistent summary of the paper is scarcely possible since the paper is in itself in a sense a summary. The following are, however, the most important points.1)Regulation may be defined as consisting in the return or approach to physiological or functional equilibrium after such equilibrium has been disturbed.2)The planarians serve as an excellent basis for the consideration of the problem of form-regulation since they exhibit various processes and degrees of form-regulation combined in various ways. Moreover, in these forms we have in many cases in the motor reactions of pieces and the relation between form-regulation and the nervous system, a clue to the character of the changes in functional conditions resulting from section and their localization.3)The processes distinguished more or less artificially as redifferentiation and regeneration can be interpreted on a functional basis and it is possible to distinguish more or less exactly the conditions which determine the occurrence of one or the other.4)Other processes of form-regulation are like these merely special cases and must be investigated as such.5)Replacement of a lost part can occur only when the functional complex remaining retains the essential conditions of the whole so far as this part is concerned. Alteration of the functional complex beyond a certain limit leads to the establishment of a new equilibrium which may be accompanied by complete reorganization, heteromorphosis, or partial or total failure to replace the part removed.ZusammenfassungEine vollständige und scharfe Zusammenfassung der Abhandlung zu geben ist kaum möglich, weil die Abhandlung in sich selbst in gewissem Sinne eine Zusammenfassung darstellt. Die wichtigsten Punkte jedoch sind die folgenden:1)Regulation kann definiert werden als Rückkehr zum physiologischen oder funktionellen Gleichgewicht oder Annäherung an dasselbe, nachdem dieses Gleichgewicht gestört worden ist.2)Die Planarien dienen zu einer vorzüglichen Grundlage für die Betrachtung des Formregulationsproblems, weil sie verschiedene Prozesse und Grade der Formregulation in mannigfacher Weise kombiniert darbieten. Überdies haben wir bei diesen Formen in vielen Fällen an den Bewegungsreaktionen der Stücke und an den Beziehungen zwischen Formregulation und Nervensystem einen Schlüssel zum Verständnis des Charakters der Veränderungen in den funktioneilen Bedingungen, die von der Schnittführung und ihrer Lokalisation herrühren.3)Die Prozesse, die mehr oder weniger künstlich als Redifferenzierung und Regeneration unterschieden werden, können auf einer funktioneilen Grundlage ausgedeutet werden, und es ist möglich, mehr oder weniger genau die Bedingungen, welche das Vorkommen des Einen oder Andern bestimmen, zu unterscheiden.4)Andre Prozesse der Formregulation sind gleich diesen rein spezielle Fälle und müssen als solche untersucht werden.5)Wiederersatz eines verloren gegangenen Teils tritt nur ein, wenn der zurückbleibende funktionelle Komplex die Hauptbedingungen des Ganzen in bezug auf diesen Teil behält. Störungen des funktionellen Komplexes über eine gewisse Grenze hinaus führt zur Aufstellung eines neuen Gleichgewichtes, welches von einer vollständigen Neugestaltung, Heteromorphosis, oder völligem Fehlschlagen der Ersatzbildung eines entfernten Teils begleitet sein kann.

Regeneration of the appendages in nymphs of the agrionidae

Some years ago the senior author noticed that the so-called tracheal gills of agrionid nymphs separate very easily from the body, and that they regenerate rapidly and completely. A few experiments showed that the legs also regenerate readily and often completely. It was suggested that the junior author make a study of the problem with a view to determining the limits and distribution of regenerative power, in the legs~ the course of regeneration and the form of the regenerated stuetures. Unfortunately it was impossible to carry the work as far as was desired, but the results obtained are of sufficient interest to warrant their presentation at this time. The work was begun in October, 1899, and continued until August, 1900, when it was interrupted. When the work was begun it was the intention to study not only the external form of the regenerating organs, but their growth and arrangement beneath the old cuticle, and the histological features of the process. The present paper, however, deals chiefly with the external form. The junior author is responsible for the observations and experiments described in the paper, the senior author for the discussions and interpretation of results. The figures represent the work of both.

ASEXUAL BREEDING AND PREVENTION OF SENESCENCE IN PLANARIA VELATA

1. Planaria velata has been bred asexually through thirteen generations in less than three years without any indications of progressive senescence in the stock. In each generation the animals have passed through the following cycle: reconstitution and rejuvenescence in the cysts, emergence as physiologically young, small animals, growth and senescence with feeding, cessation of feeding, fragmentation and encystment. During the period of breeding none of the animals have ever become sexually mature.2. Starvation and reduction being about an increase in rate of metabolism and the reduced animals after renewed feeding are in the same physiological condition as young growing animals and are again capable of growth and senescence.3. Senescence has been inhibited or so far retarded as to be inappreciable in a stock of Planaria velata during more than two years by partial starvation. During this time the animals have been kept at approximately the same size and in approximately the same physiological condition, ...

ANALYSIS OF FORM REGULATION WITH THE AID OF ANÆSTHETICS

During the last year and a half the writer has carried on an extensive series of experiments on the influence of certain anaesthetics on the course and results of form regulation in Planaria dorotocephala Woodworth. Since the method has proved to be of considerable value and since it will be some time before the results of these and other experiments planned for the future can be presented in full, it seems desirable to present briefly and without extended comment the most important features of the work up to date as an illustration of the value of the method and the results to be attained by it. In my experiments thus far I have used chiefly alcohol, ether and acetone-chloroform, known commercially as chloretone. Although alcohol is much less strongly anaesthetic than many other substances its action is in general similar in kind to that of the substances commonly known as anaesthetics. The results with the three substances mentioned are practically identical so far as the more general features are concerned, though various differences of detail appear, which need not be considered here. Incidentally, however, it may be noted that these differences in the effects of the different anaesthetics serve to some extent as a means of determining the specific differences in the effects of different anaesthetics on the metabolic processes: how far they will prove to be of value in this direction only the future can determine.

Studies on regulation: IX. The positions and proportions of parts during regulation in Cestoplana in the presence of the cephalic ganglia

Summary1.During the first thirty-five or forty days after section pieces ofCestoplana containing the cephalic ganglia increase in length, decrease in width, and gradually assume a tapering form. In later stages of the experiment a decrease in length and a relative increase in width (reverse change in proportion) occurs, although actual reduction in size is continuous.These changes in form are, like those inStenostoma andLeptoplana, primarily the result of changes in mechanical conditions accompanying the characteristic motor activity and depend largely on the use of the posterior end in a characteristic manner and the degree of motor activity. The »reverse changes in proportion« which occur during later stages of the experiments are the result of a marked decrease in motor activity.2)The new pharynx in pieces containing the cephalic ganglia always appears in a particular functional region of the body. The actual difference in its position in pieces from different regions of the body is due primarily to the different relations of the functional regions in different pieces. The position of a given functional region in a piece is determined on the one hand by the relations of that piece to the whole before section and on the other by the altered conditions consequent upon section.3)During regulation the pharynx alters its relative position, apparently moving anteriorly in the body during the earlier stages, and later apparently moving posteriorly. This apparent movement of the pharynx is not migration, but is due in part to the change in proportions brought about by mechanical conditions and in part by functional hypertrophy of the posterior region of the body during the earlier stages and its reduction in consequence of decreased function in later stages.Zusammenfassung1.Während der ersten 35 oder 40 Tage nach der Operation verlängern sich Stücke vonCestoplana, welche die Kopfganglien enthalten, unter gleichzeitiger Breitenabnahme und nehmen schrittweise eine zugespitzte Form an. In späteren Versuchsstadien tritt eine Längenabnahme und eine relative Breitenzunahme (Proportionenveränderung im umgekehrten Sinne) ein, obgleich in Wirklichkeit eine Größenverminderung bestehen bleibt.Diese Formveränderungen sind wie die beiStenostoma und beiLeptoplana primär das Ergebnis von änderungen der mechanischen Bedingungen, welche die charakteristische motorische Aktivität begleiten, und sie hängen weitgehend vom Gebrauche des Hinterendes in charakteristischer Weise und von dem Grade der motorischen Aktivität ab. Die »umgekehrten Proportionsänderungen«, welche während der späteren Versuchsstadien auftreten, sind das Ergebnis einer ausgeprägten Abnahme der motorischen Aktivität.2)Der neue Pharynx in Stücken mit den Kopfganglien erscheint immer in einem besonderen funktionellen Bezirk des Körpers. Der wirkliche Unterschied seiner Lage in Stücken aus verschiedenen Körperregionen ergibt sich primär aus den verschiedenen Beziehungen der funktionellen Bezirke in verschiedenen Stücken. Die Lage eines gegebenen funktionellen Bezirks in einem Stücke bestimmt sich einerseits aus den Beziehungen dieses Stücks zum Ganzen vor dem Durchschneiden und anderseits durch die veränderten Verhältnisse nach dem Durchschneiden.3)Während der Regulationsvorgänge verändert der Pharynx seine relative Lage, anscheinend zugunsten einer Vorwärtsbewegung im Körper während der ersten Stadien und später durch scheinbare Rückwärtsbewegung. Diese scheinbare Bewegung des Pharynx ist aber keine wirkliche Wanderung, sondern beruht teilweise auf einer änderung der Proportionen des Stückes, welche durch die mechanischen Verhältnisse und teilweise auch durch funktionelle Hypertrophie des hinteren Körperbezirks während der früheren Stadien, in den späteren Stadien durch Reduktion infolge verminderter Funktion zustande kommt.