468 DR. ST. GEORGE MIVART ON THK DEVELOPMENT [Juiie 17, 



glimmerings of light upon that most recondite and still most mys- 

 terious process, the genesis of new species 1 



We may be encouraged to hope that such a result is possible from 

 the words of one of those twin Biologists who on the same night put 

 forth their independently arrived-at views as to wiiat we are all agreed 

 to regard as at least an important factor in the Origin of Species. No 

 less a person than Mr. Wallace has written the following significant 

 words ' : — • 



" No thoughtful person can contemplate without amazement the 

 phenomena presented by tiie development of animals. We see the 

 most diverse forms — a Moliusk, a Frog, and a Mammal — arising from 

 apparently identical primitive cells, and progressing for a time by 

 very similar initial changes, but thereafter each pursuing its highly 

 complex and often circuitous course of develo[)nient, with unerring 

 certainty, by means of laws and forces of which we are totally 

 ignorant. It is surely a not improbable supposition that the 

 unknown power which determines and regulates this marvellous 

 process may also determine the initiation of these more important 

 changes of structure, and those developments of new parts and 

 organs which characterize the successive stages of the evolutions of 

 animal forms." 



These words advocate and confirm what I have elsewhere ^ ante- 

 cedently urged. 



Many influences doubtless may come into play in the origin of 

 new species ; but let us look a little narrowly at certain influences 

 which must come into play therein, aiul the action of which no man 

 can deny. 



One of these influences (which no one has more richly illustrated 

 than has the late Mr. Darwin) is that of Heredity ; but, what is 

 heredity ? 



In the first place it is obviously a property, not of new individuals 

 — not of offspring — but of parental forms. As every one knows, it is 

 the innate tendency which each organism possesses to reproduce its 

 like. If any living creature, X, was self-impregnating and the out- 

 come of a long line of self-impregnating predecessors, all existing in 

 the midst of one uniform and continuously unvarying environment, 

 then X would produce ofFsprir.g completely like itself. This fun- 

 damental biological law of reproduction may be compared with the 

 physical first law of motion^, — according to tohich any body in motion 

 will continue to move on uniformly at the same rate and in the same 

 direction until some other force or motion is impressed upon it. 



The fact that new individual organisms arise from both a paternal 

 and a maternal influence, and from a line of ancestors every one of 

 which had a similar bifold origin, modifies this first law of heredity 

 only so far as to produce a more or less complex compound of 

 hereditary reproductive tendencies in every individual ; the effect of 

 which must be analogous to that mechanical law of the composition of 



' In tlie ' Nineteenth Century,' Jan. 1880, p. 9C>. 



* ' Genesis of Species.' Macmillan, 1871. 



' My attention was called to this analogy by my friend Dr. Gasquet. 



