198 Scientific Intelligence — Zoology. 



of specific centres ; or, in other words, to believe that each species, , 

 whether of plant or animal, originated in a single birth place."* 



De Candolle has suggested twenty-seven of these independent 

 regions for plants, and the Rev. J. S. Henslow forty-five. 



For the inferior animals, D. Prichard, a distinguished Christian 

 physiologist and philosopher, proposes seven regions ; Mr Swainson, 

 five ; Professor Hitchcock, eleven ; Mr Waterhouse also eleven, but 

 with some geographical differences ; and Sir Charles Lyell, Professor 

 Agassiz, and many, if not nearly all, of the continental zoologists of 

 the present day, are united in sentiment on this principle. How 

 gratuitous — how unjust, therefore — it is to attempt to brand as in- 

 fidels those who adopt an opinion irresistibly derived from an ex- 

 amination of the truths of nature, and which has the sanction and 

 support of such names as those we have enumerated. 



It is necessary, however, to add, that most of these authorities 

 make the human species an exception, and the sole exception to this 

 doctrine of independent creations, f — Dr Morton. 



17. The Four Degrees of Hyhridity. — Hybridity, whether in 

 plants or animals, has been singularly neglected by naturalists. It 

 has generally been regarded as a unit : whereas, its facts are as 

 susceptible of classification as any other series of physiological phe- 

 nomena. Hence, I have proposed /owr degrees of hybridity, which 

 I will briefly recapitulate. 



The first degree is that in which the hybrids never reproduce : in 

 other words, where the mixed progeny begins and ends with the 

 first cross. 



The second degree is that in which the hybrids are incapable of 

 re-producing, inter se^ but multiply by union with the parent 

 stock. 



The third degree is that in which animals of unquestionably dis- 

 tinct species produce a progeny which is prolific, inter se. 



The fourth degree is that which takes place between closely 

 proximate species — among mankind, for example, and among those 

 domestic animals most essential to their wants and happiness. — Dr 

 Morton. 



18. Explanation of the rapid decrease of the Native Population 

 of Polynesia, Sfc. — The fertility of hybrid races, originating in the in- 

 termixture of two races whose affinity is most remote, is a fact of 

 which there can be no doubt whatever ; and there is strong reason to 

 believe that these hybrid races, the parents of which are Europeans on 

 one side, and the aborigines of any country on the other, are gene- 

 rally destined to become the dominant population of those countries. 

 For, on the one hand, these '* half casts" very commonly combine the 



* Prinqiples of Geology, p. 608. 



t Professor Agassiz and Ur Morton adopt the opinion of specific centres in 

 the case of man. " 



