46 



' spores * that are thrown off from the tissue of the fronds 

 of ferns, and the ' bulbels ' that drop from the axils of the 

 Lilium bulbiferum, are precisely analogous to that aggregate 

 of cells in an envelope that falls into the anterior chamber 

 of the locular uterus of the virgin Aphis : only in the plant 

 the aggregate of cells is detached from an external surface, 

 but in the animal from an internal surface. 



When it is asserted that in the propagation of the Hydra 

 by buds or by artificial division there is not ' anything like 

 oviparous reproduction/ but that it is the result of the 

 simple action of continuous growth, we feel the want of a 

 clear definition of the meaning of that phrase. In the 

 growth of the Conferva, which the reviewer rightly admits 

 to be analogous to that of gemmation, each filament ori- 

 ginates from a germ, which is first developed into a single 

 cell ; this cell increases, and it either divides, or its germ- 

 granules give origin to two cells within it, which take the 

 place of the former ; and by the repetition of this increase 

 and multiplication a long and single series of tubular cells, 

 attached at one end, free and constantly growing at the 

 other, is at last produced, as linger and other mycologists 

 have clearly demonstrated. 



Now, short of the mere formal and non-essential modi- 

 fication of the juxtaposition of the cells, end on end, the 

 process here described is the same as that with which the 

 development in ovo of the mammal, and doubtless also of 

 Man himself, begins : the germ-cell gives origin to two ; 

 these new cells themselves undergo the same increase by 

 subdivision, which is repeated through a long series of cell- 

 generations until a coherent mass or body of countless cells 

 is produced, which differ from those in the Conferva, inas- 

 much as they are in contact with each other at many and 

 indefinite points, instead of being arranged in a linear series. 



The first step in the formation of the bud in the Hydra, 

 as in the Ccenurus, is the multiplication of cells, which also 

 are aggregated together as in the ovum, and not set end on 



