566 BULLETIN OF THE 



any pulmonate mollusk as he has shown in Figs. 4 and 5. These irregularly 

 conical, pointed projections of hyaline protoplasm may sometimes attain two 

 fifths the length of the radius of the yolk, and the larger ones exhibit prolonga- 

 tions of the granular vitelline substance for a little distance into the central 

 portion of their bases. They are normally radial in position, but are easily 

 distorted by manipulation of the egg. The only motion which he has recog- 

 nized has been a slight displacement of the granules mentioned, doubtless 

 caused, he thinks, by unobserved changes in the form of the cones. These 

 persist for a comparatively long time ; but they are at length contracted into 

 knoblike processes with narrow pedicels, and then entirely disappear. " Their 

 presence coincides with that of the system of radiations which succeeds the 

 germinative vesicle, and they are always retracted within the yolk before the 

 escape of the first polar globule." They recall that which Fol has named 

 the " cone d'exsudation " in the egg of Asterias. " But I am able to affirm 

 that, with Helix, there never exists between these hyaline cones and sperma- 

 tozoa the relations which this savant has attributed to them in the case of 

 the echinoderms." 



The pseudopodia which were seen in Limax (Fig. 95) were limited to the 

 region of the animal pole, were much lower and more rounded, and occurred 

 at a later stage, than those seen by Perez in Helix. 



Fol's ('79) finely illustrated memoir on " Fecundation," etc., besides con- 

 sidering more fully than any of his preliminary papers the events of matura- 

 tion and fecundation, contains extensive bibliographical abstracts and criticisms, 

 a chapter on segmentation, and the discussion of several topics of theoretical 

 interest. 



The author's observations were made on representatives of echinoderms (As- 

 terias, Sphserechinus, Toxopneustes), worms (Sagitta), and mollusks (Ptero- 

 trachea). 



In Asterias the germinative vesicle, " nucleus de I'ovule," is composed of a 

 liquid portion surrounded by a viscid, semi-fluid limiting layer, which does 

 not merit the name of membrane, in the ordinary sense of the word. Hard- 

 ened in alcohol or one of numerous acids, the liquid part of the nucleus of a 

 mature ovarian ovule is surrounded by a membrane presenting a double con- 

 tour. This does not warrant the conclusion that a membrane exists in the 

 living egg, but only that the vesicle is limited by a layer which coagulates 

 differently from the surrounding vitelline substance. The discussion as to 

 whether this layer belongs to nucleus or vitellus is useless. It is only to be 

 determined by tracing its origin. This is difficult in the germinative vesicle, 

 but not in the female pronucleus. The latter is formed — ^both its con- 

 tents and its limiting envelope — in the midst and at the expense of the vi- 

 tellus. " Nucleus " embraces both the envelope and the contents. The fluid 

 contents are traversed by a network of sarcodic filaments uniting two layers 

 of like substance, one of which lines the envelope within, while the other 

 surrounds the germinative dot. The filaments hold in suspension pale, sparse 

 granules of variable magnitudes. With the use of reagents a greater number 



