Frank R. Lillie

Physiology of Development of the Feather V. Experimental Morphogenesis

TABLE OF CONTENTS PAGE

POLARITY AND BILATERALITY OF THE ANNELID EGG. EXPERIMENTS WITH CENTRIFUGAL FORCE

In a previous paper (Lillie, †? oA3) I attempted to show that the direction of polarity of the egg of C/icetopterus is not modified by any experimental redistribution of the visible elements, nucleus and granules, and I therefore concluded that polarity is a property of the ground substance of the protoplasm. In the present paper I propose to examine the grounds for this statement, to attempt to show that bilaterality comes in the same category, and to examine the conceptions of polarity and organization that naturally result.

ON THE DEVELOPMENT OF FEATHERS

I. Feather papillae are regarded as individually persistent throughout life, from the time of their origin between the sixth and ninth days of embryonic life. In each feather tract the order of origin is significantly related to dynamic field properties of the tract, such as growth rates, degrees of asymmetry, etc.

STUDIES OF FERTILIZATION IX. ON THE QUESTION OF SUPERPOSITION OF FERTILIZATION ON PARTHENOGENESIS IN STRONGYLOCENTROTUS PURPURATUS

The statement of Loeb (1913, p. 234; 1915, p. 260—261) that eggs of Strongylocentrotus purpuratus which have formed mem branes as a result of butyric acid treatment can be fertilized with sperm if the membranes are destroyed by shaking raises a diffi cult question in the problem of fertilization. It is known that eggs in which membranes have been formed by spermatozoa are incapable of refertilization, even if the membranes are destroyed by shaking immediately after their formation. We have every reason to believe that the membrane-forming reaction by butyric acid is the same as by fertilization. The after effects should therefore be the same. In an examination of this problem in the case of Arbacia, C. R. Moore (1916) showed that this is the case, viz: that, given a full membrane reaction by butyric acid, the eggs became in capable of fertilization, even if the membranes are removed. It is, however, possible to superimpose fertilization on an inconi pletereactioncausedby butyricacidto a variableextentwhich is roughly proportional to the degree of the original reaction. Just (1919) investigated the same problem in the case of Echinarachnius parva, and determined that eggs which have formed full membranes after butyric acid treatment do not re spond to subsequent insemination whether the membranes are removed or not. The writer took advantage of the opportunity afforded by a stay at the Hopkins Marine Station in Pacific Grove, California, in January and February, i9@o, to repeat Loebs experiments on the same species that he used. The results obtained diverged