6 RIPE OVARIAN OVUM. 



with the same care as Gotte, but it is difficult to believe that 

 an extrusion of the vesicle in the way described by Oellacher 

 would have escaped his notice. 



Passing from Vertebrates to Invertebrates, we find that 

 almost every careful investigator has observed the disappear- 

 ance, apparent or otherwise, of the germinal vesicle, but that 

 very few have watched with care the steps of the process. 



The so-called Richtungskorper has been supposed to be the 

 extruded remnant of the germinal vesicle. This view has been 

 especially adopted and supported by Oellacher (Jioc. cit), and 

 Flemminsf \ 



The latter author regards the constant presence of this body, 

 and the facility witli which it can be stained, as proofs of its 

 connection with the germinal vesicle, which has, however, 

 according to his observations, disappeared before the appear- 

 ance of the Richtungskorper. 



Kleinenberg ''^j to whom we are indebted for the most pre- 

 cise observations we possess on the disappearance of the germ- 

 inal vesicle, gives the following account of it, pp. 41 and 42. 



" We left the germinal vesicle as a vesicle with a distinct doubly 

 contoured membrane, and equally distributed granular contents, in 



which the germinal spot had ai)peared The germinal vesicle 



reaches O'OGmm. in diameter, and at the same time its contents under- 

 go a separation. Tlie greater part withdraws itself from the membrane 

 and collects as a dense mass around the gei'miiial spot, while closely 

 adjoining the membrane there remains only a very thin but unbroken 

 lining of the plasmoid material. The intermediate space is filled 

 with a clear fluid, but the layer which lines the membrane retains 

 its connection with the mass around the germinal vesicle by means 

 of numerous fine threads which traverse the space filled with fluid. 



At about the time when tlie formation of the psendocells in the 



eg^ is C(jmpleted the germinal spot undergoes a retrogressive meta- 

 morphosis, it loses its circular outline and it now appears as if 

 coagulated ; then it breaks up into small fragments, and I am fairly 



confident that these become dissolved. The germinal vesicle 



becomes, on the egg assuming a sj)herical form, drawn into an 

 eccentric position towards the pole of the egg directed outwards, 

 where it lies close to the surface and only covered by a very thin 

 layer of plasma. In this situation its degeneration now begins, 

 and ends in its complete disap})earance. The granular contents 

 become more and more fluid ; at the same time part of them pass 



1 Studicn in dcr Entwicklungsgcschichtc der Najudcn, Sitz. d. k. Akad. 

 Wien, Bd. lxxi. 1875. 



2 Hydra. Leipzig, 1872. 



