in the Animal Kingdom. ^ 119 



seem to hold a middle place between " Shoots,"" on the one hand, 

 and " Germinal Vesicles," on the other.* 



The ovum of more elaborate structures, perhaps of all the 

 rest of the animal kingdom, is a sac, containing a sort of Yolk, 

 the Germinal Vesicle, and a Layer of granules. (Fig. 1. 

 p. 120.) 



The Yolk of ova generally, is very much the same in essential 

 character ; but performing a more important part in some ani- 

 mals than in others, it differs much in quantity. 



The Germinal Vesicle is an exceedingly delicate, transparent 

 sac; measuring in diameter sometimes less than T D th of a 

 line,-f- and containing a pellucid fluid. On the internal surface 

 of the Germinal Vesicle, there has lately been discovered an opa- 

 city, the Germinal Spot (Macula germinativd), consisting of 

 extremely minute granules, more or less spherical in form. 

 With a magnifying power of eight hundred diameters, that is 

 to say, magnified 640,000 times, this spot has not yet been 

 found to consist of other than homogeneous parts.J It has been 

 already said, that it is contained within the Germinal Vesicle; the 

 latter measuring in diameter sometimes less than T J s th of aline. 



In some Infusoria, the contents of the Germinal Vesicle are 

 rather a mass of granules, than a fluid and a spot ; perhaps cor- 

 responding parts, in a less concentrated state. Indeed, may not 

 " Shoots," " Germinal Granules," and the contents of the Germi- 

 nal Vesicle, be, all of them, corresponding parts, in different 

 states of concentration ? 



The Layer of Granules (Germinal layer), containing per- 

 haps, in part, the rudiments of the future Germinal Membrane, 

 lies immediately on the internal surface of the Primary Mem- 

 brane that contains the Germ and Yolk. This layer is more or 

 less circumscribed, often indistinct, because of its periphery 

 coalescing with the Yolk. The Germinal Vesicle is found 

 lying in the centre of this layer of granules, on the surface of 

 the Yolk ; though there are reasons for supposing that, origi- 

 nally, the Germinal Vesicle is situated in the centre of the Yolk. 



Purkinje, in Berlinerworterbuch, Band x. S. 109. 



| Wagner, in Ed. Med. and Surg. Journ. 1836. No. 127- 



$ Wagner^ 1. c. 



