BLASTOGENIC VARIATIONS. 169 



from their remote ancestors. . . Some of the hybrids 

 in make and disposition strongly suggest their zebra 

 sire, others their respective dams; but even the most 

 zebra-like in form are utterly unlike their sire in their 

 markings." In some respects, also, the hybrids were 

 intermediate between their parents. 



As to the causes of the different relationships be- 

 tween parental and hybrid characters, we are almost 

 entirely in the dark. Weismann has endeavoured to 

 account for them on his theory of the germ-plasm, but 

 his explanation is purely theoretical and from its nature 

 incapable of experimental verification. The observa- 

 tions of the author on sea-urchin hybrids, and of Pro- 

 fessor Ewart on crosses between varieties of rabbits, 

 throw a little light on the subject, for they show that 

 the characters of the hybrids may be considerably in- 

 fluenced by the seasonal condition of the parental sex- 

 cells, and thereby seem to indicate that the compara- 

 tive degrees of nutrition of the sex-cells, and perhaps 

 also of their constituent parts, may be a very important 

 factor. One should also bear in mind that, as was 

 demonstrated by Mendel in the case of certain plant 

 hybrids, some of the parental characters may remain 

 latent in the hybrid offspring, and only reveal their 

 presence in subsequent generations. The existence of 

 latency is also shown by secondary sexual characters. 

 In every female all the secondary male characters, and 

 in every male all the secondary female characters, ap- 

 parently exist in a latent state, ready to be evolved 

 under certain conditions, such as the removal of the 

 ovaries or testes. The variability of hybrids may there- 

 fore be due not only to their having received varying 



