120 Dr Barry on the UnKy of Structure 



We have then 



Istly, " Shoots ;" as in many Zoophyte?. 



&%, " Germinal Granules ;" a half-fluid granulous mass, as 

 in some Infusoria, some Polypes, and many other Zoophytes. 



3<%, The ova of some Infusoria, in which the Germinal 

 Vesicle contains a mass of granules. 



4thly, Perfect ova, of more elaborate animals, viz. 



Fig. 1. 

 .a Germinal Spot. 



b Fluid contained in Germinal Vesicle. 



c Germinal Vesicle. 



d Layer of granules, having the Germinal Vesicle in its centre. 



Yolk. 



/ Primary membrane, enclosing the Germ and Yolk. 



5thly, Superadded, in Mammals and in Man, there are the 

 Graafian Vesicle, and its fluid,* viz. 



* In Mammals, and in Man, the part corresponding to the ovum of other 

 animals, is called the ovulwn. 



For the discovery of the latter, an epoch in the history of development, 

 we are indebted to the illustrious Von Bar. Von Bar was once a pupil of Db'l- 

 linger, the head of the Wiirzburg School ; who having expressed to the former 

 a wish, that some young naturalist^should, under his own superintendence, 

 thoroughly investigate the development of the common fowl, Von Bar would 

 most gladly have undertaken it, but for circumstances that required for a time 

 his estrangement from the subject. Von Bar mentioned it, however, to his 

 friend Pander, who had come to Wurzburg, at his suggestion, to be a fellow, 

 pupil of Dollinger. Pander undertook those researches ; and hence his dis- 

 covery of the primary separation of the Germinal Membrane into layers. 

 Von Bar returned with renewed ardour to the subject, and discovered the 

 Ovulum of Mammals ; Purkinje having in the mean time found the Germi- 

 nal Vesicle of Birds. Valentin next discovered the Germinal Vesicle in 

 Mammals ; and Wagner afterwards found the Germinal Spot. The last-men- 

 tioned author justly asks, Is this spot also to present some contained part? 



For a particular account and drawings of these minute bodies, sec Von Bar, 

 " de Ovi Mammalium et Hominis genesi ;" also the Ed. Med. and Surg. Journ. 

 Nos. 127 and 128 ; and MUller's Archiv, 1836, Heft ii. ; likewise a paper by 

 Purkinje, " Symbolse ad Ovi Avium historiam ante incubationem ;" and one 

 by Bernhardt, " Symbolae ad Ovi Mammalium historiam ante prsegnationem." 



Dr Allen Thornton, one of the very few in this country who have attended 

 to the subject of development, has given an epitomized but very comprehen- 

 sive account of the changes in the Germinal Membrane of Vertebrated Ani- 

 mals, so far as ascertained up to the time when he wrote (1830), adding ob- 

 servations of his own. (See vols. ix. and x. of this Journal.) 



