396 BULLETIN OF THE 



latter does, a single nucleolus with a minute fluid-filled space. The 

 most natural explanation of the case would then be, that the spermato- 

 zoa observed and figured within the yolk had not led, up to the time 

 of observation, to a real fecundation ; * that the description of the 

 metamorphosis of the "germinative vesicle," as elsewhere (p. 278) given 

 in extenso, relates to that vesicle rather than any other nuclear struc- 

 ture ; but that the author overlooked the formation of polar globules, 

 and assumed that the condition of every unsegmented egg found to 

 present some stage of the rosette figure must have resulted immediately 

 from the metamorphosis of the germinative vesicle, rather than through 

 the intervention of any other nuclear body. 



The changes of the " germinative vesicle " of the fecundated egg de- 

 scribed by FoL ('73) for Geryonia have been given elsewhere (p. 279), 

 since they relate to the nucleus of the first cleavage-sphere, not to the 

 germinative vesicle. The metamorphosis of the latter escaped him. The 

 " Faltenstern " of the egg membrane is supposed by the author to indi- 

 cate the spot where fecundation takes place ; but I think it is more 

 likely that it is connected with the formation of polar globules, of which 

 the author usually saw one.f What that intimate relation is which the 

 polar globule in other ccelenterates sustains to the act of fecundation, 

 the author does not say. One is inclined to believe that he looked 

 for an orifice J out of which the polar globule had come, and through 

 which the spermatozoa had penetrated into the egg. 



Balbiani ('73, p. 84) denies that there exists in spiders any connection 

 between the nuclei of the blastoderm cells and the Purkinjean vesicle. He 

 adds nothing to our knowledge of the metamorphosis of this structure. 



BuTSCHLi ('73% p. 101, Taf XX VI. Fig. 61*^, i. -iv.) unquestionably 

 saw and figured what is now known as the female pronucleus, but was 

 unable to give positive information concerning its origin. It makes its 

 appearance as a clear vesicle, at the pole of the egg which is directed |l 

 toward the vagina, some time after the germinative vesicle has ceased to 

 be visible. Whether the latter is ejected, or simply has become 



* The observation of unaltered spermatozoa within the yolk gives reason to sus- 

 pect that the egg here figured was not capable of normal development. 



t " Vermuthlich entspricht der Faltenstern der Stelle wo die Befruchtung stattfand. 

 Hier befindet sich in der Hiille fast constant ein Korn oder Richtungskorperchen 

 von 15 - 20 /i Grosse. Ein ahnliches Korperchen, welches mit dem Befruchtungsacte 

 in naherer Beziehung zu stehen scheint, habe ich auch bei anderen Coelenteraten 

 beobachtet." (p. 475.) 



t " Eine Oefifnung ist beim befructeten Ei hier [i. e. at the Faltenstern] nicht zu 

 entdecken." 



