in Organized Beings. Ill 



velopment in the same organism, but by the study of their 

 gradual development in the animal scale. 



I have now sketched an outline of the doctiine of Unity of 

 Function with regard to the changes essential to the mainte- 

 nance of individual oi'ganisms, both of plants and animals ; we 

 may next briefly direct our attention to the reproductive sys- 

 tem, and examine how far it is from the first a special appara- 

 tus, and whether its functions are completely separated in any 

 case from those of the nutritive organs. In tracing the deve- 

 lopment of the reproductive organs in the cellular plants, we 

 observe that in the lowest tribes the multiplication of cells may 

 be considered as alike the production of new individuals and 

 the extension of the original organism ; each cell is capable of 

 maintaining an independent existence, but each is connected 

 with those around it in forming one general structure. Where 

 special reproductive vesicles are evolved, different from the 

 cells which form the plant, we find that at first no particular 

 part of the general surface is modified for their development ; 

 but in the higher algae, the lichens, and especially the fungi, 

 we can trace the gradual separation of the reproductive from 

 the nutrient system. In the flowering plants we have still two 

 modes of reproduction ; the special apparatus of fructification 

 furnishing seeds ; and the nutritive system furnishing buds, 

 which may be regarded as extensions of the original stock, or 

 as new individuals. The doctrines of Morphology, however, 

 prove to us that even the fructifying system is but a different 

 form of corresponding parts in that of nutrition ; and hence 

 the separation is never complete in vegetables. In the lowest 

 animals, we may remark a similar difficulty in fixing the pre- 

 cise limits of individuality ; and this is a necessary result of the 

 gradual specialization which this function undergoes in common 

 with every other. Where distinct gemmules are formed, (which 

 in their homogeneity resemble the spores of cellular plants,) 

 they are at first produced from any part of the external surface, 

 as in the hydra ; but in ascending the scale we find a particu- 

 lar apparatus adapted to the evolution of the embryo, such as 

 the curious ovaries of the echinoderma. As we advance, the 

 structure of the ovum becomes more and more complex, and 

 the analogy which its parts bear to tliose of the seeds of plants 



