40 Dr Martin Barry's Researches in Embryology. 



which arises the new being ; an opinion which, as will pre- 

 sently be shewn, is that of Keber also."* 



Keber describes the penetration of the spermatozoon into 

 the interior of the ovum in Unio and Anodonta, through an 

 aperture formed by dehiscence of its coats, analogous to the 

 micropyle in plants ; and he refers to an observation in ova 

 of several species of Holothuria made by Professor Johannes 

 Miiller, and communicated by him to the Academy of Berlin 

 in 1850 and 1851, of what he (Miiller) considered as very 

 much resembling that micropyle. The orifice found by Keber 

 to form for the entrance of a spermatozoon into the Mussel's 

 ovum, seems to correspond to that seen by myself to have 

 formed for the same purpose in the ovum of the Rabbit ; in 

 which orifice I saw and delineated what I believe to have 

 been the head-like extremity of a spermatozoon on the point 

 of uniting its hyaline nucleolus with that of the germinal spot. 

 Neither Keber nor Nelson, it is true, saw any such immediate 

 and close connection between the fecundating element and the 

 germinal spot. Nor do I think that this was essential, seeing 

 that in the ova they examined, the yelk enters largely into 

 the formation of the new organism; while in the mammiferous 

 ovum (the subject of my observations) it is the fecundated 

 germinal spot alone that forms it. Hence they did not trace 

 the fecundating element beyond the yelk. Nelson describes the 

 spermatozoa as undergoing liquefaction in the yelk, the ger- 

 minal spot furnishing the nuclei to effect cleavage of the latter. 

 Keber saw the spermatozoon, or rather what he terms the nu- 

 cleus of its head-like extremity, to divide into nucleoli in the 

 yelk. He acknowledges his inability to solve the question, in 

 what relation these nucleoli derived from the spermatozoon 

 stand to the pell acid nuclei of the yelk-balls; which nuclei — ac- 

 cording to Vogt, Von Baer,Loven, Johannes Miiller, and others 

 — have their origin in the germinal spot-t But after recapitu- 

 lating the results obtained, he concludes from the observations 

 of Johannes MiillcrJ and his own, that neither the germinal 



* Eveti Nil on, however, was not aware of my having recorded the penetra- 

 tion of the spermatozoon into the ovum as an established fact ; though Keber 

 Wto fully aware of it, and does me the justice to quote all that I had written in 

 the ]'ni/"?f,j, Ideal Tr6n#dctt#rh on the subject; both in 1840 and 1843. 



t Kel er ; toe, cit , p. 40. ♦ Muller'e Archiv, 1852. 



