GENESIS. 221 



inferior animals devoid of special reproductive organs, such 

 as the Hydra, the ova and spermatozoa originate in the 

 layer of indifferent tissue that lies between the endoderm 

 and the ectoderm ; that is, they consist of portions of the 

 least specialized substance. And in the higher animals, 

 these same generative agents appear to be merely modified 

 epithelium- cells — cells not remarkable for their complexity 

 of structure, but rather for their simplicity. If, by 



way of demurrer to this view, it is asked why other epithe- 

 lium-cells do not exhibit like properties ; there are two replies. 

 The first is, that other epithelium- cells are usually so far 

 changed to fit them to their special functions, that they are 

 unfitted for assuming the reproductive function. The second 

 reply is, that in some cases, where the epithelium- cells are 

 but very little specialized, they do exhibit the like properties : 

 not, indeed, by uniting with other epithelium- cells to produce 

 new germs, but by producing new germs without such union. 

 I learn from Dr Hooker, that the Begonia phyllomaniaca 

 habitually develops young plants from the scales of its stem 

 and leaves — nay, that many young plants are developed by a 

 single scale. The epithelium- cells composing one of these 

 scales, swell, here and there, into large globular cells ; form 

 chlorophyll in their interiors ; shoot out rudimentary axes ; 

 and then, by spontaneous constrictions, cut themselves off; 

 drop to the ground ; and grow into Begonias. It ajypears, 

 too, that in a succulent English plant, the Malaxis paludosa, 

 a like process occurs : the self- detached cells being, in this 

 case, produced by the surfaces of the leaves. Thus, 



there is no warrant for the assumption that sperm-cells and 

 germ-cells possess powers fundamentally unlike those of 

 other cells. The inference to which the facts point, is, that 

 they differ from the rest, mainly in not having undergone 

 modifications such as those by which the rest are adapted to 

 particular functions. They are cells that have departed but 

 little from the original and most general type. Or, in the 

 words suggested by a friend, it is not that they are peculiarly 



