aOO M. E. Claparede on the Theory of the 



Mammalia." And elsewhere — " It is consequently proved that 

 Newport has the honour of having discovered this curious and 

 unexpected phsenomenon of the penetration of the spermatozoid 

 into the ovum, as the result of its own movements. This has 

 nothing to do with the micropyle or anything of the kind ; but 

 these singular organic elements possess the property, by means 

 of their so-called tail, of exerting so considerable a mechanical 

 effect as to enable them to traverse the layer of albumen and the 

 vitelline membrane." Further on again — " I assert therefore 

 that I was wrong in the opposition which I made to Dr. Barry, 

 who is certainly the first who saw a spermatozoid in the interior 

 of an egg in general, and of a mammalian ovum in particular, 

 and to him belongs the honour of this discovery." 



Bischoff here attributes to Barry only the discovery of the 

 presence of zoosperms in the ova, and not that of their pene- 

 tration, because he still denies that this penetration takes place 

 in the manner described by Barry, Nelson and Keber, although 

 he does not dispute the presence of the micropyle in the Ano- 

 dontcB. The penetration of the spermatozoa into the ova of the 

 Babbit and Frog, as also the presence of the micropyle in those 

 of the Anodontay when once sanctioned by Bischoff, could not be 

 again called in question ; for it certainly must have been a dis- 

 agreeable task for the celebrated embryologist to retract his opi- 

 nion, after having declared that the penetration of the zoosperms 

 into the ovum could only be maintained by the merest novices 

 in embryology. We owe him all the more gratitude for having 

 thus placed himself above the suggestions of self-esteem, and 

 publicly confessed his own error. 



From the publication of this ^' Confirmation " we may date the 

 epoch in which the existence of the micropyle has obtained a 

 definite place in our physiological knowledge. Nevertheless, 

 even if we suppose that Barry did not see a true micropyle, the 

 honour of the discovery does not pass to Keber. As we have 

 stated, Leuckart had mentioned the micropyle a little while 

 before him, and given an exact history of its formation precisely 

 in the Unios and Anodons, a history which he has since com- 

 pleted*. According to him, the ovarian vesicles of the Naiades 

 consist of a tolerably thick structureless membrane, on the inner 

 surface of which, instead of a proper epithelium, there is a layer 

 of fatty molecular corpuscles, united by a tenacious albuminous 

 mass. It is in this layer that the germinal vesicle with its cha- 

 racteristic spot is first formed. This vesicle, with the mass of 

 albumen which surrounds it, soon forms a swelling or lump 

 on the inner surface of the ovarian vesicle. This gradually in- 



* Zusatz zu Bischoff'sWiderlegung. 



