564 BULLETIN OF THE 



place. As stated above, these nuclei have, in his opinion, an entirely different 

 origin. The signification of the enlargements remains to be discovered, but 

 they do not appear to him to be in all cases essential. Concerning received 

 opinions about the formation, division, and migration of the nuclear plates, and 

 their conversion into nuclei, he says : " Cette interpretation n'est nullement 

 conforme aux faits observes par moi chez I'Helix, et que je viens d'exposer. 

 Sans nier d'une maniere absolute cette marche des radiations [?] du fuseau vers 

 les sommets de ce corps, bien que je n'aie rien observe de semblable, je dois 

 declarer qu'il n'existe pas veritablement de plaque nucleaire chez I'Helice. 

 Existat-elle d'ailleurs chez cet animal, on ne saurait lui attribuer la production 

 des noyaux du systeme radiaire, dont I'origine est toute autre, ainsi que je 

 crois I'avoir demontre." 



Perez thinks Auerbach, Biitschli, and Strasburger are wrong in making the 

 nuclei arise in the spindle, and not at the centres of the asters, and explains 

 as the cause of their error that they have not witnessed the origin of these 

 structures. When the nuclei are advanced in age, the dynamic influence which 

 they exert on the surrounding protoplasm ceases, and they then move a little 

 toward the equator. Manipulation and reagents may also cause or exaggerate 

 this peculiarity. These, then, are the sources of error into which he thinks 

 previous observers have fallen ! 



The mistakes of Perez already pointed out, and his failure to discover the 

 nuclear plate, are, I believe, chargeable with all this subversion of the real order 

 of events, and to the same account must be attributed his misconception of the 

 nature of the polar globules. I need not repeat the proof, which is entirely in- 

 contestable, of the cellular nature of these globules, and will only state briefly 

 the position defended by the author. These globules are formed just as de- 

 cribed by Robin, with the exception that the second is produced like the first, 

 and is not, as Robin maintained, already formed before elimination. There is 

 nothing in Perez's description or figures of this stage which is not to be seen in 

 the living egg. It is, then, not surprising that the globules are considered as 

 only two drops of the disintegrated radial substance which once surrounded 

 the "stellar nuclei," and that neither the spindle nor the half of it escapes as 

 such from the yolk. It is not sufficient that he tells us he has " followed at- 

 tentively the phenomena," and has " endeavored to discover that which these 

 savants have described." There is no evidence that he has used in these stages 

 the means necessary for the discovery of the things they have described, and it is 

 therefore to no purpose that the assertion is made, " Leur structure n'a rien de 

 I'element cellulaire, et ils ne naissent point comme lui." He has " been able 

 to recognize neither the spindle nor the two suns between the production of 

 the first polar globule and that of the second." " It appears that with this 

 mollusk there does not remain in the vitellus a single trace of radiate proto- 

 plasm after the emergence of the two polar globules." The figures which I 

 have given for Limax show how probable it is that Perez has overlooked some 

 of the stages in the formation of polar globules in Helix. 



In his opinion, the radiate substance surrounding the vesicular nuclei having 



