298 M. E. Claparede on the Theory of the 



merit of having called attention to the micropyles of the ova of 

 the Anodonta, which are so easily found, that it is sufficient to 

 pass the scalpel over an ovary and place what it takes up under 

 the microscope in order to see them in great numbers^ this would 

 be something ; but its greatest merit undoubtedly was its ener- 

 getically inducing the combat. Thus, Bischoff, although appa- 

 rently a protector of the quarto volume in two languages, inas- 

 much as it was dedicated to him, could not avoid taking up the 

 pen to put Keber's inexperience into its proper place, not with- 

 out some brusqueness. It was not so much Keber, he said, as 

 Newport, and especially Nelson, that he came forward to refute ; 

 few would be led astray by the verbiage of the former, but the 

 others were philosophers of a much more serious character. 

 Indeed Nelson^s observations appeared to have nothing impro- 

 bable about them, to those who were acquainted with the works 

 of Siebold* and Thaerf upon the Trematode worms, and those 

 of Max SchultzeJ and Leuckart§ upon the Turbellaria. These 

 authors have proved that in these hermaphrodite animals, besides 

 the vas deferens which leads from the testicle to the penis, there 

 is a second canal which passes directly to the place where the 

 eggs are formed at the point of union of the canals coming from 

 the vitellogene and the germigene || ; from which it might be con- 

 sidered probable that the spermatozoids passing through the 

 second deferent canal may be enclosed in the ovum at the 

 moment of its formation, so as to fecundate it at once, although 

 these authors did not observe anything of the kind. Bischoff 

 then took upon himself to refute Barry, Nelson, Newport and 

 Keber. The latter had no strength for the struggle and was 

 soon overthrown. The vibratile vesicles {Wimperblasen) which 

 he had taken for eggs gave him the finishing stroke. 



Leuckart^ on his side had undertaken to show how the mi- 

 cropyle is formed in the Naiades ; he had ascertained that it was 

 nothing but the peduncle which attaches the young ovum to the 

 stroma of the ovary, and which afterwards tears away, still 

 retaining the form of the neck of a bottle. T. von Hessling** 



* MuUer's Archiv, 1836. t Ibid. 1850. 



X Naturgeschichte der Turbellarien. Greifswald, 1851. 



§ Troschel's Archiv, xviii. 



II Or rather from the ovary and the albumen-gland. J. Midler has in 

 fact proved that the so-called germigene contains perfectly complete eggs, 

 so that the vitellogene must descend again to the rank of albuminogene. 

 Siebold himself, who gave these glands the names of vitellogene and ger- 

 migene, appears now to have returned to this opinion. 



^ Zusatz zu BischoflPs Widerlegung. He had moreover previously de- 

 scribed this formation of the micropyle. — Handworterb. der Physiol, iv. 

 Article Zeugnng. 



** Zeitschrift fiir wiss, Zoologic, April 1854. 



