102 



HYPOTHESIS OF THE DEVELOPMENT OF 



mammifers ; and even the serpent tribes, which present 

 no external appearance of such extremities, possess them 

 in reality, but in an undeveloped or rudimental state. 



The same law of development presides over the vegeta- 

 ble kingdom. Amongst phanerogamous plants, a certain 

 number of organs appear to be always present, either in a 

 developed or rudimentary state ; and those which are 

 rudimentary can be developed by cultivation. The flow- 

 ers, which bear stamens on one stalk and pistils on another 

 can be caused to produce both, or to become perfect flow- 

 ers, by having a sufficiency of nourishment supplied to 

 them. So also, where a special function is required for 

 particular circumstances, nature has provided for it not by 

 a new organ, but by a modification of a common one, 

 which she has effected in development. Thus, for in- 

 stance, some plants destined to live in arid situations, 

 require to have a store of water which they may slowly 

 absorb. The need is arranged for by a cup-like expan- 

 sion round the stalk, in which water remains after a 

 shower. Now the pitcher, as this is called, is not a new 

 organ, but simply a metamorphose of a leaf. 



These facts clearly show how all the various organic 

 forms of our world are bound up in one — how a fundamen- 

 tal unity pervades and embraces them all, collecting them, 

 from the humblest lichen up to the highest mammifer, in 

 one system, the whole creation of which must have de- 

 pended upon one law or decree of the Almighty, though 

 it did not all come forth at one time. After what we have 

 seen, the idea of a separate exertion for each must appear 

 totally inadmissible. The single fact of abortive or rudi- 

 mentary organs condemns it ; for these, on such a suppo- 

 sition, could be regarded in no other light than as blem- 

 ishes or blunders — the thing of all others most irreconcil- 

 able with that idea of Almighty Perfection which a gene- 

 ral view of nature so irresitibly conveys. On the other 

 hand, when the organic creation is admitted to have been 

 effected by a general law, we see nothing in these abor- 

 tive parts but harmless peculiarities of development, and 

 interesting evidences of the manner in which the Divine 

 Author has been pleased to work. 



We have yet to advert to the most interesting class of 

 facts connected with the laws of organic development. It 

 is only in recent times that physiologists have observed 

 that each animal passes, in the course of its germinal his- 



