Miscellaneous. 159 



formed, that the male asters show themselves, each at a little 

 distance from the spot where a zoosperm has penetrated. Several of 

 the radiating filaments extend from the centre of the star to the 

 point of the surface of the vitellus where the contact took place, a 

 point which is still recognizable by the presence of a small scar. 

 It is no doubt these filaments that M. 0. Hertwig has mistaken in 

 the urchin for the tail of the spermatozoid. 



The male asters gain in distinctness as they depart from the 

 margin of the vitellus ; and in their centre is formed a little mass of 

 protoplasm, which we may call a male pronucleus. The male pro- 

 nucleus nearest to the female pronucleus amalgamates with the 

 latter, which immediately becomes the centre of a system of radiating 

 filaments ; then this combined nucleus unites again with a second, 

 and sometimes even with a third, male pronuclei;s. At other times 

 the female pronucleus divides, at the very moment of its formation, 

 into two or three fragments, which then unite with so many male 

 centres. The male asters never unite with each other ; it would 

 appear that they repel one another and are attracted by the female 

 centre until the moment when the latter is neutralized by its union 

 with two or three male centres. 



The segmentation of these ova is very irregular. ^\'Tien the male 

 centres are numerous the vitellus forms at once as many rounded 

 bosses as it contains male asters, each boss having an aster in its 

 centre ; then these bosses become spherules, which continue 

 dividing dichotomously. From this results a very irregular blasto- 

 sphere and a monstrous larva. 



In cases in which the number of male centres in very restricted, 

 and the female pronucleus is divided into two or three nuclei, these 

 alwaj's remain distinct. At the moment of the first segmentation 

 each becomes converted into an amphiaster, and the vitellus divides 

 at once into four or six spherules. I have not observed the seg- 

 mentation in the ova, the single nucleus of which is the result of 

 the combination of the female pronucleus with several male asters. 

 Perhaps we must refer to this category the ova (which I have often 

 met with) in which the nucleus is at once resolved into a tetraster — 

 that is to say, four asters united to each other. 



Can a vitellus which has received two zoosperms be developed in 

 a normal manner ? I do not venture to deny this absolutely ; but I 

 have always observed the contrary ; I have always seen these ova 

 produce a double number of segmentation-spherules, and finally 

 become monstrous larvae. Is not this fact fitted to put us on the 

 track of a whole category of double monsters ? 



Analogous phenomena are presented in ova fecundated at matu- 

 rity, but proceeding from animals which have suffered in captivity. 

 IIa\dng fecundated some ova derived from a very sickly parent, I saw 

 the zoosperms penetrate in numbers into each viteUus, and their 

 bodies remain intact in the midst of the vitelline substance, although 

 they were surrounded by some ill-marked radiating lines. They all 



