392 BULLETIN OF THE 



fecundation. De Quatrefages ('48) indicates very clearly that the ger- 

 minative vesicle disappears in w?zfecundated eggs (p. 171) of Hermella, 

 but also that the " clear space " which occupies the yolk previously to 

 the elimination of the "globule transparent" (polar globule) in eggs 

 already fertilized is no longer visible after the formation of that globule. 

 He is uncertain whether the disappearance of the germinative vesicle is 

 accomplished in the same manner in both cases. Although he thinks 

 Bischoff speaks too positively in saying that there is no definite relation 

 between the time of the vesicle's dissolution and either the escape of the 

 egg from the ovary or the act of fecundation (pp. 173, 174), still he ulti- 

 mately (p. 181) leaves this question in an undecided condition. 



Other observers have answered with sufficient positiveness, but their 

 conclusions have differed widely. While in the opinion of many the dis- 

 appearance of the vesicle followed fecundation as its immediate result, 

 others have as positively denied such a causal relation. 



Already in 1827 Von Baer maintained that the migration and disap- 

 pearance of the germinative vesicle was a phenomenon of the ripening 

 of the egg,^ an opinion which he has since taken occasion to reiterate. 

 (See Von Baer '35, pp. 4, 9, and '37, pp. 28, 157, 297.) The same con- 

 clusions have been reached by many other observers upon all classes of 

 animals. 



Reichert, on the contrary ('46, pp. 199, 205), evidently looks upon the 

 disappearance of the vesicle as the first result of impregnation in the 

 case of Strongylus, and Krohn ('49, p. 5, foot-note) dissents from Derbes's 

 opinion ('47, p. 83), when the latter makes the germinative vesicle (sphere 

 moyenne) in Echinus disappear before fecundation, and ascribes the sup- 

 posed error to want of careful study. Krohn himself observes the absence 

 of the vesicle and dot half an hour after fecundation (p. 7). 



In 1853 Leuckart ('53, pp. 921, 922) thus summarized earlier opin- 

 ions : " As a rule the disappearance of the germinative vesicle is consid- 

 ered as the immediate result of fecundation." But, on the strength of 

 the evidence before him, he did not hesitate to draw this conclusion : " If 

 we put all these facts together, then it really can hardly remain longer 

 doubtful, that the disappearance of the germinative vesicle characterizes 

 a process which belongs more to the formative history of the egg than 

 to the history of the development of the subsequent embryo." There 

 are, nevertheless, many who have still insisted on the essential impor. 



* *' Vcsiculam PurJcinji partem ovi efficacem esse credo, qua facultas feminina vim 

 exerceat, ut facultas masculina semini inest virili. Vesiculse igitur protusio et disso- 

 lutio ab ovi maturitate et forsan irritatione penderent." (Von Baer '27, p. 29.) 



