MUSEUM OF COMPARATIVE ZOOLOGY. 239 



The description thus far evidently relates to the formation and migra- 

 tion of the structure called in the present paper the first archiamphi- 

 asteVf and to the method of its production from the clear spot which 

 succeeded the Purkinjean vesicle. Although revealing none of the 

 finer structural changes which have recently been brought to light, this 

 description leaves no doubt as to the nature of the object, nor the sub- 

 stantial accuracy, of the observations. The same cannot, however, be 

 said regarding some of Warneck's subsequent statements. One does 

 not, at least, feel the same certainty that the author has before him this 

 archiamphiaster phase of development when he says (p. 119) that the 

 difference between Limax and Lymnseus consists only in this, that each 

 sphere in the case of the latter possesses a thick envelope with two dis- 

 tinct contours. This statement does not agree with that already cited, 

 declaring the spheres to have a thin envelope. The discrepancy is 

 probably due to Warneck's having confused the asters with pronuclei, 

 in which event the case of spheres with double contour must have been 

 such as is really found only at a later period, viz. after the formation of 

 the polar globules. It seems unreasonable that so accurate an observer 

 should have made such a mistake, and yet I do not see any other possi- 

 ble explanation. It would be entirely unreasonable to suppose that the 

 archiamphiaster in Lymnaeus possessed double contour lines, even if the 

 convincing studies of Biitschli on this genus were wanting. What is 

 said relative to the vesicles found in these nuclear spheres may well 

 be referred to the pronucleoli. 



In Warneck's opinion (pp. 121, 122) these two nuclear spheres remain 

 quite passive during the formation of the polar globules, which takes 

 place from the pole of the yolk toward which the spheres have migrated. 

 This process is described at some length. 



Fol, it is true, finds authority in Warneck for saying that one of these 

 nuclear spheres escapes under the form of globules, — the excretory (or 

 direction) corpuscles.* The only passages allowing such an interpre- 

 tation are the ones already quoted, but the subsequent statements of 

 Warneck are so entirely unequivocal that I cannot hesitate in believing 

 his conception to have been quite unlike that which Fol ascribes to him. 

 Warneck says (p. 120) that there appears between the outer rim (i. e. 



say that the polar globules are produced by the elimination of one of the nuclear 

 spheres. On the other hand, he states, in the most positive manner, that the polar 

 globules have nothing to do with these nuclear spheres. (See below. ) 



* "Cette tache se divise en deux moities, dont I'une reste au centre du vitellus, 

 tandis que I'autre arrive a la surface, et sort sous forme de globules : les corpuscles 

 excretes (ou de direction)." (Fol, '75% p. 22.) Compare also Fol, op. cit., p. 26. 



