180 OVARY AND PAROVARIUM, BY W. WALDEYER. 



however, depicts a young cell of the ovum with two nuclei ; 

 but in the ripe ovum a double germinal vesicle does not appear 

 to have been at any time observed. 



The nucleolus, or macula germinativa, is never absent 

 in the primordial egg 1 . It has a dull or finely granular appear- 

 ance, and as I, with v. la Yalette (117), am disposed to think, is 

 of a solid nature ; though Schrb'n (103) considers it to be a 

 vesicle. On the addition of distilled water, the germinal spot 

 disappears (v. la Yalette, 117). The presence of two germinal 

 spots in one germinal vesicle has often been noted, as, for ex- 

 ample, by R. Wagner (130), in the Cockchafer ; subsequently 

 by v. la Valette (117) in the larva of the Dragonfly, and still 

 more recently by Claparede (131), in the Earthworm, in which 

 it is of constant occurrence. In this case the two germinal 

 spots, of which one is constantly much larger than the other, 

 are united to form a twin spot. 



In addition to the germinal spot, a few small round cor- 

 puscles are sometimes found in the germinal vesicle, the signifi- 

 cance of which has not as yet been ascertained. If, with v. la 

 Valette (117) and Pfliiger (84), we regard the germinal spot as 

 a precipitate from the germinal vesicle, we may give a similar 

 explanation of their nature. 



The germinal spot only remains persistent in the ripe ova of 

 Mammals ; in all other Yertebrata it disappears at a very early 

 period, and in its stead a cloudy finely granular mass appears 

 in the germinal vesicle, through which several bright globules 

 are distributed, especially in Batrachia and Fishes. The period 

 at which the germinal spot disappears cannot be precisely 

 fixed. 



Schron has recently described a still smaller bright and apparently 

 solid body within the germinal spot, to which he has given the name 

 of " Granule " (Korn). I have not hitherto been able to discover it 

 in Mammals, but it is constant in many of the lower animals, as, for 

 example, in the Ascaridae, though here perhaps it may turn out to be 

 the smaller part of Claparede's twin spot (see fig. 193, E and F). 

 V. la Valette (117) considers the granule of Schron to be a vacuole, 

 and does not find it to be of constant occurrence. Balbiani (9) differs 

 most widely in his views on this point from the others. He describes 



