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vesicle, and in course of time became condensed about it. 

 Mr. Desor had, he said, noticed similar appearances in the 

 ovarian egg of Nemertes and Ascidia. The egg of the 

 latter is at first merely a transparent cell, containing the 

 germinative vesicle, about which, at an early stage of devel- 

 opment, a cloud of small granules seems to be forming. 

 These granules are probably cells. As the process goes on, 

 the surrounding area becomes crowded with them, but they 

 are the most numerous near the germinative vesicle. At a 

 later stage the granules recede from the circumference of 

 the sphere, to become compact about the germinative ves- 

 icle, forming the perfect yolk, and leaving the surrounding 

 space filled with a transparent fluid. This liquid has been 

 hitherto regarded by embryologists as albumen. As Mol- 

 lusks, however, have no oviduct in which albumen could be 

 formed, this cannot be its true character. Mr. Desor had 

 therefore been led to the conclusion that it is a true 

 " mother liquid," from which the yolk has been precipitated, 

 crystallized, as it were. It must for this reason be the most 

 important part of the ovum, and accordingly he proposes 

 for it the name " Biogen liquid.^^ The facts observed in 

 the development of Mammalia strongly inclined him to the 

 opinion that this process of precipitation from the Biogen 

 liquid would be found to be universal. Bischoff has figured 

 the Rabbit's ovum surrounded by the chorion, with the 

 whole of the enclosed space filled up by the yolk. As 

 development goes on, the yolk is found not to occupy the 

 whole interior, but it is occupied in part by a clear fluid, 

 which surrounds the yolk, the nature of which BischofF 

 acknowledges he is at a loss to understand. This, Mr. 

 Desor suggested, is probably the Biogen liquid. Thus it 

 would appear that all yolks are formed by condensation : a 

 fact of great interest, indicating as it does, that the great 

 law of attraction is at the bottom of the formation of 

 organic, as well as inorganic bodies; and that the same 

 force which has condensed the heavenly bodies, acts with 



