CHAPTEE V. 



BLASTOGENIC VARIATIONS (Continued). 



Reversion; commonest in crossed races, as of the pigeon and fowl; its 

 theoretical explanation Prepotency; in the trotting horse and in 

 man; probably due in large part to inbreeding Mendel's Law of 

 Hybridisation, and its range Natural and artificial plant hybrids 

 Animal hybrids Sports; probably of different origin to normal 

 variations Artificial production of monsters Telegony ; probably 

 non-existent Parthenogenesis in an Ostracod and in Daphnia 

 Does sexual reproduction induce variability? Relation of varia- 

 bility of individual to variability of race Asexual reproduction in 

 plants Bud-variation. 



IN the last chapter we saw that the average char- 

 acters of offspring are inherited from their ancestors in 

 accordance with a simple and definite law, but it re- 

 mains for us to discuss several phenomena related to 

 this law, some of which, indeed, appear to afford a par- 

 tial contradiction of it. These are the phenomena of 

 reversion, prepotency, the appearance of sports, and 

 certain cases of hybridism. The variations which show 

 themselves in connection with such phenomena, though 

 doubtless of less importance than those already dis- 

 cussed, are nevertheless in some instances considerable, 

 and of not infrequent occurrence. They therefore 

 merit a fairly full discussion. It is impossible, how- 

 ever, to illustrate this with many exact numerical data, 

 simply because these do not exist. One must as a rule 

 remain content to quote the descriptive evidence of 



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