8G 



THE ZOOLOGIST. 



establish a connection between the mode of raising domesticated 

 races and the cause or causes to which wild animals owe their 

 differences. He instanced the alternate generations of the sea- 

 jellies, and the reproduction of the Salpae, and added that there 

 are far more astonishing phenomena than the slight differences 

 produced by the intervention of man among domesticated ani- 

 mals, and which would shake their belief in such differences 

 being trustworthy indications of the variability of species. 

 Agassiz held that animals and plants could not have sprung 

 from a single centre of creation, but were created where they 

 now are; and with regard to each new species in successive 

 strata, " Nature made him, and then broke the die." 



[Since the publication of the 1 Origin of Species ' much has 

 been done by Darwin and others at home, and much by the 

 numerous band of Evolutionists abroad, to illustrate variation in 

 animals. In Britain, Bateson held that variation — continuous 

 and discontinuous — indeed, offered the best chance of explaining 

 evolution, and his laborious work is well known. According to 

 Galton great deviations are less common than slight deviations. 

 The Mendelian theory, again, which has sprung into prominence 

 lately chiefly by the labours of Bateson, is thought by some to 

 be the theory which will solve the riddle of Evolution. Briefly, 

 Mendel's law of inheritance in hybrid varieties holds that if a 

 well-established form, with a definite character, e.g. size or 

 colour, be crossed with another in which the character is diffe- 

 rent, the offspring will usually resemble one of the parents in 

 the distinguishing character which is " dominant," the character 

 remaining latent being " recessive." If the hybrids are crossed, 

 the descendants will be of two kinds, some like the dominant, some 

 like the recessive. When those like the recessive parent are crossed 

 only recessives are bred. When those like the dominant parent are 

 crossed the results are pure dominants, and apparent dominants, 

 that is, with power to produce more pure dominants, more pure 

 recessives, and more apparent dominants. The two characters 

 do not combine in successive generations, and their antecedents 

 occur in the germ-cells. More complex phenomena, however, 

 occur in other cases, as e. g. in the breeding of fowls with single 

 comb, rose-comb, and pea-comb. Thus when pea is crossed with 

 single comb it acts as dominant. When pea is crossed with rose- 



