Fecundation of the Ovum, 293 



the Rabbit. Important as this assertion was, it did not make 

 much noise in the world. Barry's discovery passed again into 

 the shade and no one took it up on the Continent. BischofF* 

 contented himself with mentioning it repeatedly as erroneous 

 and describing it as a mere product of the imagination [Geburt 

 der Phantasie), 



For twelve years Barry's discovery slumbered. At the end of 

 this time one of his countrymen, also a good observer. Dr. Nel- 

 son t, of Glasgow, revived the question by publishing an obser- 

 vation analogous to that of Barry, although relating to a very 

 different animal, — an intestinal worm, the Ascaris of the Cat 

 {Ascaris mystax). According to Nelson the ova of this worm, 

 at the period when fecundation takes place, are entirely destitute 

 of vitelline membrane, and possess no envelope of any kind. 

 They are, generally, triangular, or rather pyramidal in form, in 

 consequence of their being pressed against one another in the 

 oviduct. Nevertheless their margins are sufficiently well marked, 

 in consequence of the cohesion of the yelk : at one of the angles 

 alone the outline is less distinct, for which reason Nelson gives 

 this angle the name of the ^^ broken edge.'' After copulation, 

 the spermatozoids, which, in consequence of their form, the 

 author denominates " spermatic cells," penetrate into the ovi- 

 duct, reach the ova and insinuate themselves into the substance 

 of the vitellus. According to Nelson, this penetration of the 

 spermatozoids into the ovum takes place at any point of the sur- 

 face, and even at several points on the same ovum at once ; but 

 he remarks that the spermatozoids appear to prefer the " broken 

 edge" for this purpose. As soon as they are in the e^^, the 

 '^ spermatic cells " begin to disappear, probably by dissolution, 

 and their place is occupied by a transparent liquid. In this 

 phasnomcnon consists the whole system of fecundation. The 

 ovum immediately begins to undergo modifications. The vitellus 

 acquires a spotted appearance, previously noticed by Reichert 

 in Strongylus, and considered by that anatomist as the result of 

 the formation of cells in the interior of the yelk ; the existence 

 of these cells in this Ascaris is completely denied by Nelson. 

 The germinal vesicle bursts, and its disappearance is immediately 

 followed by a modification of the granules of the vitellus, which 

 become transparent. After this transformation Nelson proposes 

 to give them the name of embryonal granules. In the interior 

 of the f^^^j a cell with a nucleus and nucleolus is formed ; these 

 are the blastodermic vesicle and spot. Whilst these things are 



* Entvvickelungsgescliichte (les Kanincheneies, 1842, — des Ilundeeies, 

 1845, — des Meerscliweincliens, 1852. 

 t Phil. Trans. 1852, part 2. 



