of the Development of the Ovum of the Rabbit. 45 



thought himself enabled to pronounce the disappearance of 

 the germinal vesicle in Mammals, also, " as a decided fact," 

 he now, in 1842, after seeing my papers, acknowledges (p. 39) 

 that " very probably the nucleus of the germinal vesicle [i. e. 

 the germinal spot] is the essential part, which first of all ex- 

 periences the influence of the coitus, namely a mixing with 

 the seminal fluid." [I had shown the centre of the altered 

 germinal spot to be the 'point of fecundation.^ 



Bischqff, p. 56. — " I have certainly several times observed 

 in the yelk a part more pellucid than the rest, the presence of 

 which undoubtedly is of great importance." This probably 

 was not the germinal vesicle, but an early state of the twin 

 successors of it. (See my figs. 187, 191, 193, in plate 24, Phil. 

 Trans. 1840.) — I have at this time several ova in a state nearly 

 resembling these, which have been preserved for many weeks 

 by means of the putty ring; the entrance of the air having 

 been further prevented by a cement consisting of gold size 

 (Lein-oel Firniss) and a little lamp-black. 



Bischqff, fig. 1. — What Bischoff describes as cells of the 

 membrana granulosa, appear to have been cells of the central 

 part of the retinacula. [The retinacula will be found exceed- 

 ingly distinct in the Ferret — Mustela Furo ; which animal I 

 selected when showing these structures to Professor Owen.] 



Bischqff] fig. 2. — " Fleckiges Ansehn." The same appear- 

 ance will be found represented by myself in the Phil. Trans. 

 1840, plate 24, figs. 188, 189; and the cause producing it is 

 described in p. 541 of that volume (§ 357). 



Bischqff, fig. 6. — The five so-called small yelk-balls appear 

 to have been cells, that had not undergone that liquefaction 

 which removed the other cells in the layer of which they had 

 formed a part. 



Bischqff, fig. 16. — Mistakes blood-corpuscles for cells of 

 the so-called "discus," which, after becoming club-shaped, 

 he supposes to have returned to their previous form. [The 

 ovum had lain in water ! p. 54.] 



Bischqff, figs. 19, 20. — Mistakes the incipient chorion for a 

 deposit of albumen. 



Bischqff, p. 61. — Says nothing on the subject of a fact to 

 which I directed particular attention; viz. that, on pressure 

 being applied, the young chorion becomes elliptical. Is this 

 to be expected of mere albumen ? [Bischoff had previously 

 said — Wagner's Physiologie, p. 96 — "most certainly the 

 ovum receives in the oviduct no new covering ; it receives no 

 layer of albumen and no i schalenhaut,' like the ovum of the 

 ovipara."] 



Bischqff, fig. 17. — Mistakes solitary cells, not yet liquefied, 

 for " Nachkommen des Keimfleckes." 



