George Newport

On the Nervous System of the Sphinx ligustri, Linn., (Part II.) during the Latter Stages of Its Pupa and Its Imago State; And on the Means by Which Its Development is Effected

In a former paper I have described the anatomy of the nervous system of the Sphinx ligustri, Linn ., and the changes it undergoes during the larva and the earlier stages of the pupa states. In the paper which I now have the honour of laying before the Society, these changes will be followed through the remaining stages, until the insect has arrived at its full development, and I shall endeavour to show the manner in which they are effected.

On the Impregnation of the Ovum in the Amphibia. (First Series)

The communication which I have now the honour to present to the Royal Society is a portion of a series of investigations on the Development of the Embryo on which I have been for some years engaged, and which was commenced in a paper on the Development of the Myriapoda, that was honoured with a place in the Philosophical Transactions for 1841. I now propose to give the results of my observations on the Amphibia, reserving to a future early occasion the continuation of those on the Invertebrata commenced in the paper alluded to. The Amphibia, of all the vertebrated animals, afford to us the readiest means of investigating the difficult subject of Impregnation by actual experiment, and it is only, perhaps, by combining experiment with careful observations on the physical conditions that affect the development of the germ, and comparing these with the facts of the natural history and instincts of the species, that we may hope, ultimately, to obtain some further insight into this one of Nature’s most hidden secrets.

On the Nervous System of the Sphinx ligustri, Linn., and on the Changes Which It Undergoes during a Part of the Metamorphoses of the Insect

In this paper it is proposed to describe the development and arrangement of the nerves, and the changes which they undergo, in the Sphinx Ligustri, Linn., during the last stage of the larva, and the earlier stages of the pupa state. The labours of that industrious naturalist Heroldt have already shown us, to a certain extent, in what manner similar changes occur in the Papilio Brassincæ Linn.; and therefore the author of the present essay would not have ventured to trespass upon the attention of the Royal Society, were it not that these changes are capable of more minute explanation than those which take place with such rapidity in the P. brassicæ. But the Sphinx ligustri, Linn., remaining as it does for several months in an apparently torpid condition, between its larva and perfect state, allows us an opportunity of more deliberately observing in what manner the changes are effected; while the superior bulk of the insect enables us to trace them with greater precision.

The Bakerian Lecture: On the Organs of Reproduction, and the Development of the Myriapoda. First Series

The development of the Myriapoda has hitherto been only partially investigated. It is, nevertheless, a subject of great importance to the comparative anatomist, from the remarkable fact that it takes place in a manner entirely different from that of most of the higher Articulata, to some of which the Myriapoda are closely allied both in habits and structure. The true Insecta arrive at their perfect state by an aggregation or apparent diminution in the number of their segments, but the Myriapoda, on the contrary, by a repeated increase of these parts, which in many instances are multiplied to several times their original number. This addition of segments, during the growth of the animal, occurs throughout the whole class, and is one of its chief characteristics. This fact was first noticed long ago by Degeer, but since the period of his observations nothing further was added to our knowledge until it was fully confirmed by the careful investigations of Savi, and also by the more recent labours of Brandt, Gervais, and Waga. But excellent as are the observations of these naturalists, some of the most important circumstances connected with them have been entirely overlooked, both as regards the condition of the embryo on leaving the ovum, and also as regards the manner in which the new segments are developed. M. Gervais has pointed out a circumstance in which the Scolopendradæ differ from the Iulidæ in the development of the legs, but no precise account, so far as I have been able to ascertain, has been given of the production of the segments. In the observations which I now have the honour of submitting to the Royal Society, I propose, first, to examine the organs of reproduction, and then to show the various changes as they occur in the development of lulus terrestris, one of the commonest species of the Iulidæ of this country. The reproductive parts in Iulus are exceedingly interesting on account of their simplicity of structure. Treviranus has described them in the male as two elongated tubes which terminate in separate orifices behind the seventh pair of legs, without any external organ of intromission. In the female, he says, they are composed of a long ovary, formed of two knots of eggs which extend from its outlet in the fourth segment, to its termination beneath the alimentary canal, near the anus; but in this account he has entirely overlooked the essential parts of these organs in both sexes.

On the Structure, Relations, and Development of the Nervous and Circulatory Systems, and on the Existence of a Complete Circulation of the Blood in Vessels, in Myriapoda and Macrourous Arachnida. First Series

The increasing importance that is daily attached to the study of the comparative anatomy of the Invertebrata, and the interest with which every microscopic examination of structure is now regarded, as assisting to elucidate the great problems of life in the higher animals, have encouraged me through several years to prosecute a series of investigations, in the articulated classes, on two of the most important portions of the body,—the nervous and circulatory systems. These investigations have afforded me, from time to time, some interesting results, part of which, on one of these structures, I have already had the honour of communicating to the Royal Society. I now propose to communicate the results of my examinations of both these structures, and to illustrate their development, and the relations which they bear to each other, in some of the principal classes, commencing, in the present paper, with the Myriapoda and Arachnida. The objects to which my attention has been directed in this paper are three:—First, the minute anatomy of the nervous system in the Myriapoda and Macrourous Arachnida, more especially with regard to the structure of the cord and its ganglia, and the means which these afford us of explaining the physiology of the nervous system, and the phenomena of the reflected movements in articulated animals. Secondly, to demonstrate the existence of a complete system of circulatory vessels in the Myriapoda and Arachnida. Thirdly, to show the identity of the laws that regulate the development of the nervous and circulatory systems in these Articulata, and their dependence on the changes which take place in the muscular and tegumentary structures of the body, as I formerly showed in regard to the changes in the nervous system of insects.

XXIV. On the respiration of insects

It has been long proved by many physiologists that insects produce the same changes in the atmosphere during respiration as other animals. Reaumur, Bonnet, Scheele, Huber, Edwards, Audouin, and others, have all shown that the results of the respiration of atmospheric air by insects are the production of carbonic acid gas, and the loss of oxygen; but these results vary in degree in different genera,—in the different states of the same insects, —and at different periods of the year. My object, therefore, in this paper will be to show the relative quantity of air consumed by different tribes of insects in their different states, —the power which particular insects have of supporting existence in different media, -—and the relation which this power and the consumption of air bear to the comparative volume of the structures concerned. The life of an insect has been considered by naturalists to have three distinct periods, the larva, the pupa, and the perfect state; but each of these periods, in so far as the functions of the different structures of the body are concerned, although tending only to the production of the perfect individual, is in itself a distinct condition. Thus the respiration, circulation, temperature, food, and locality of the insect are in general all different in the different states. In the earliest period of the larva state the respiration is much feebler than when the animal has nearly arrived at its full size, and the circulation of its blood is much quicker; but the relative quantity of its food is much greater, in proportion to its bulk, in the latter than at the earlier period, and its power of generating heat increases as it approaches to its adult condition, In the pupa state also there is a change in all these functions. In many genera the insect ceases to eat; its circulation becomes slower than at any other period; its respiration is greatly diminished in frequency and volume; and its power of generating and of maintaining a temperature of body above that of the surrounding medium, which every individual insect constantly preserves when in a state of activity, is now almost suspended. In the perfect, or imago, state there are other changes in these functions. The respiration again increases in frequency and volume; the power of generating and of maintaining heat is very much augmented; the circulation is more rapid than at any other period, while the necessity for a constant supply of food is often less urgent than in the larva state. Hence it is evident that much caution is necessary in drawing conclusions from our observations on the function of respiration in insects in their different states, and that where quantity of air is concerned the relative volume of the organs of respiration must not be forgotten.