528 Royal Society— Jyw Martin Barry's 



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 

 contents of the germinal yesicle thus enter into the formation of 

 two cells. The membrane of the germinal vesicle then disappears 

 by li(iuefaction. 



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 liquefaction, 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 i)ropagation continue the 

 same with reference to number only. The process inherited from 

 the germinal vesicle by its twin offspring, reappears in the progeny 

 of these. Every cell, whatever its minuteness, if its interior cari 

 be discerned, 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 globular. 



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

 cells, aj)pears by no means to be limited to the period in question. 

 Thus it is very common to meet with several varieties of epithelium - 

 cells in the oviduct, including those which carry cilia, filled with 

 cells ; but the whole embiyo at a subsequent period is composed 

 of cells filled with the foundations of other cells. 



In the second series of these researches, it was showTi that the 

 mulberry-like object above mentioned, is found to contain a cell 

 larger than the rest, elliptical in form, and having in its centre a 

 thick-walled hollow sphere, which is the nucleus of this cell. It 

 was further shown that this nucleus is the rudimental embryo. From 

 what has been just stated, it appears, that the same process, by 

 which a nucleus in one instance transforms itself into the embryo, 

 is in operation in another instance, where the product does not ex- 

 tend beyond the interior of a minute and transitory cell. Making 

 allowance, indeed, for a difference in form and size, the description 

 given of the one might be applied to the other. It was shown in 

 the second series, that in the production of the embryo out of a 

 nucleus, layer after layer of cells come into view in the interior, 

 while layers previously formed are pushed further out ; each of the 

 layers being so distinctly circumscribed as to appear almost mem- 

 branous at its surface. The same membranous appearance presents 

 itself at the surface of the several layers of a nucleus in many situa- 

 tions. Further, in the formation of the embryo, a pellucid centre 

 is the point around which new layers of cells continually come into 

 view ; a centre corresponding to that giving origin to similar ap- 

 pearances in every nucleus described in the present memoir. It was 



