OWEN'S THEORY. 319 



"germ mass." (Plate VI., figs. 4, 5, 6, 7, 8.) In the 

 Conferva, instead of a mass, a thread of cells has arisen, 

 forming the filament which constitutes the whole plant. 

 In the animal, the cells are not placed end to end, 

 thread-like, but side to side, and form what is called 

 the " mulberry mass '' (fig. 8) ; and a further dis- 

 tinction is to be noted, namely, that each animal cell, 

 as it formed, carries with it a portion of the yolk. 

 From the '' germ mass " the animal is evolved. Each 

 cell of this mass is the offspring of the primary germ- 

 ceU, reproducing its powers and capacities. Since the 

 animal is formed out of this mass, and by means of it 

 (figs. 9, 10), we are forced to the conclusion that the 

 cells have become transformed into tissues. But " not 

 all the progeny of the primary germ-cell are required 

 for the formation of the body in aU animals : certain 

 of the derivative germ-cells may remain unchanged, 

 and become included in that body wdiich has been 

 composed of their metamorphosed and diversely com- 

 bined or confluent brethren : so included, any deriva- 

 tive germ-cell, or the nucleus of such, may commence 

 and repeat the same processes of growth by imbibition, 

 and of propagation by spontaneous fission, as those to 

 which itself owed its origin.'' * 



It is this, according to Owen, which constitutes Par- 

 thenogenesis. Some of the cells, instead of being 

 transformed into tissues, remain, unchanged as cells, 

 included in the body, where they rej^eat the original 

 process of subdivision, and produce offspring as they 



* Owen : Parthenogenesis, p. 5. 



