168 BOARD OF AGRICULTURE. 



in the ova of the queen-bee, and in the preceding section we 

 have shown that the ovum is in essentials an animal cell. The 

 connection between the gemma and the cell may not be so 

 well indicated in some cases as in the hydra, where the gemma 

 thrown off are not merely structurally, but functionally com- 

 plete ; but it is clearly indicated in the zoospores of an ulva 

 or conferva, where the gemma appears but a cell, yet has the 

 inherent capacity of development into the parent species. 



The act of generation is but the union of two cells, the 

 sperm and the germ, whereby a new being is the result. The 

 process in itself is not different in its principles from the other 

 methods of reproduction, but differs in the results following 

 its application. In all cases the only requisite for reproduc- 

 tion is the presence of a sufficiency and variety of force to 

 originate and support the process we call vital. In simple 

 cells there seems to be this force present, apparently in a ratio 

 with the age of the cell. As we attain complexity of envi- 

 ronment for certain cells the forces at work, or sufficient for 

 reproduction in the simply-constituted cell, are in part used up 

 in meeting and responding to the changes produced by added 

 complexity, and less is available for the production of new 

 cells like themselves, and reproduction is retarded in propor- 

 tion as demands are made on the vital forces for other pur- 

 poses. This antagonism between the nutritive (self-preser- 

 vation) and the generative (self-propagation) functions has 

 been generally remarked upon by physiologists, and is to be 

 explained by the doctrine of persistence of force. 



When the force inherent is sufficient for preparing the cell 

 for development, and yet cannot compel the development 

 further of itself, on account of the weakening of some of its 

 forces through expenditure in sustaining the equilibrium 

 between itself and other forces, we may have reproduction by 

 gemmation, the cell cast forth meeting with new forces in its 

 career, which its inherent vitality enables it to appropriate for 

 its own use, and through the added force extend its own 

 development. Thus the egg of the queen-bee cannot hatch 

 the drone except food be supplied it ; and the force within 

 the egg when laid only enables it to develop the grub, a par- 

 tial transformation towards the completed insect, for the pur- 

 pose of appropriating and using the forces stored in the food 



