16 Dr Barry'^s jResearthes in FMhryolog^, 



the thick transparent membrane of the ovum in some instances 

 appears to have become attenuated, in others also cleft. Sub- 

 sequently, the central portion of the altered spot passes to the 

 centre of the germinal vesicle ; the germinal vesicle, regaining 

 its spherical form, returns to the centre of the ovum, and a 

 fissure in the thick transparent membrane is no longer seen. 

 From these successive changes, it may be inferred that fecun- 

 dation has taken place ; and this by the introduction of some 

 substance into the germinal vesicle from the exterior of the 

 ovary. It may also be inferred, that the central portion of 

 the altered germinal spot is the point of fecundation. In fur- 

 ther proof that such really is the case, there arise at this part 

 two cells, which constitute the foundation of the new being. 

 These two cells enlarge, and imbibe the fluid of those around 

 them, which are at first pushed further out by the two central 

 cells, and subsequently disappear by liquefaction. The con- 

 tents of the germinal vesicle thus enter into the formation of 

 two cells. The membrane of the germinal vesicle then disap- 

 pears by liquefaction. 



Each of the succeeding twin cells presents a nucleus, which, 

 having first passed to the centre of its cell, resolves itself into 

 cells in the manner above described. By this means, the twin 

 cells, in their turn, become filled with other cells. Only two 

 of these in each twin cell being destined to continue, the others, 

 as well as the membrane of each parent-cell, disappear by li^ 

 quef action, when four cells remain. These four produce eight, 

 and so on, until the germ consists of a mulberry-like object, 

 the cells of which do not admit of being counted. Nor does 

 the mode of propagation continue the same with reference to 

 number only. The process inherited from the germinal vesi- 

 cle by its twin offspring, reappears in the progeny of these. 

 Every cell, whatever its minuteness, if its interior can be dis- 

 cerned, is found filled with the foundations of new cells, into 

 which its nucleus has been resolved. Together with a doubling 

 of the number of the cells, there occurs also a diminution of 

 their size. The cells are at first elliptical, and become glo- 

 bular. 



The above mode of augmentation, namely, the origin of cells 

 \xk cells, appears by no means to be limited to the period in 



