Miscellaneous. 435 



vesicle. We shall, like H. Fol, call it \h.G female pronucleus. This 

 nucleus always appeared to me smaller than the nucleolus of the 

 e^g — an observation which appears to me difficult to reconcile with 

 the opinion of 0. Hertwig. Moreover I have frequently met with 

 ova in which the Wagnerian spot was no longer visible, and in which 

 the female pronucleus did not yet clearly present the nuclear ap- 

 pearance. On the other hand, it is incorrect to say that the female 

 pronucleus has no genetic connexion with the nucleolus of the oviale, 

 seeing that the substance of that nucleolus, mixed with that of the 

 germinal vesicle, serves for the formation of the first amphiaster, 

 which gives birth to the female pronucleus. 



By examining, without reagents, a great number of eggs recently 

 deposited and not yet fecundated, we observe very interesting facts. 

 The egg presents two little cumuli of a protoplasm clearer than the 

 rest of the vitelline mass. These two cumuli may be variously 

 placed with respect to each other ; but very generally they are placed 

 at the extremities of one diameter. One of them originates at the 

 expense of the brother star of the female pronucleus ; this star forms 

 an unequal caryolytic figure, the small star of which becomes the 

 cumulus in question ; this cumulus, lastly, produces the first polar 

 globule ; the second originates subsequently from the first. The 

 polar globules are very small in the urchin, and, moreover, they 

 disappear very rapidly ; lastly, they do not remove far from the 

 surface of the vitellus, and it is therefore possible that in Toxo- 

 pneustes lividus they may have escaped the notice even of so prac- 

 tised an observer as 0. Hertwig. 



I have said that in order to make these observations it is neces- 

 sary to take recently deposited eggs : the deposition may be induced 

 at will in several ways. The same phenomena may also be observed, 

 however, in ova taken directly from the genital gland ; but in opera- 

 ting thus we are exposed to a source of error. In fact, with the 

 liquid of the perivisceral cavity a certain number of the amoeboid 

 elements which float in that liquid are very frequently removed ; 

 and these elements, by attaching themselves to the surface of the 

 vitelline membrane, which is intimately applied to the vitellus, may 

 simulate vitelline cumuli or even polar globules. All confusion is 

 avoided by taking deposited eggs, and following them step by step 

 for some time up to the moment of fecundation. 



As soon as the egg is brought into contact with the spermatozoids, 

 the latter apply themselves by their heads over the whole periphery 

 of the membrane, and impress upon the vitelline sphere a very rapid 

 gyratory movement. The vitelline membrane, hitherto very close 

 to the surface of the viteUus, separates from it by degrees ; and, in 

 consequence, the second cumulus, the apex of which adheres to the 

 membrane, is drawn out into a cone, uniting the vitellus to the 

 surface. As no spermatozoid is seen to penetrate between the vitel- 

 line membrane and the vitellus, round which there exists a large 

 clear space, I incline to think that the second cumulus serves for 

 the passage of the spermatozoid, either by the apex of the cone ter- 

 minating at a pore in the membrane, or (which appears to me more 

 probable) by the fecundating act consisting essentially in a diff"usiou 



