6S Proceedings of the Boy at Physical Soc 



amount of the material it can convert. According to Pfeffer 

 in his " Physiology of Plants " (4), their production is regu- 

 lated in connection with the stage of development arrived 

 at, as well as by stimulus from external agency, and " the 

 production and excretion of enzymes exhibit a regulatory 

 connection with one another, as is indeed the case with 

 every metabolic function." 



In the union of gametes a further complication is induced, 

 a doubling of the qualities in the germ cell. All the cells, 

 from this onward, have the double qualities imposed upon 

 them. For each correlated property or function, formerly 

 present in the gamete, a couple to it is presented, which may 

 be like it from identical inheritance, or may differ from 

 it more or less in degree. The experiments in breeding by 

 Mendel, Evvart, Bateson, and others, have shown that these 

 couples may segregate, or separate again, when gametes are 

 once more produced, and it is inferred that this is brought 

 about by a halving of the qualities in sporogenesis or gameto- 

 genesis. The halves of these couples are termed allelomorphs 

 by the authorities on these experiments, and in this case the 

 allelomorphs are said to have segregated (5). In other cases, 

 however, it is noted that segregation may be incomplete or 

 absent, and it is considered that there may be, in some cases, 

 a breaking up of the allelomorphs, followed by recombina- 

 tion. Again, when the allelomorphs are unlike one another, 

 it is found that one may show itself in the animal or plant 

 in undiminished intensity, or even exceed it, or, on the other 

 hand, may be intermediate in character, or some character 

 may present itself which is unlike either. In the first case 

 the character is said to be " dominant," while the one that 

 does not show itself is said to be " recessive." The work of 

 Bateson (6), coupled with these experiments, has demonstrated 

 that variation is usually, or perhaps always, more or less dis- 

 continuous in origin. They have also produced strong 

 evidence for what was first insisted upon by Weismann, 

 viz , that variation arises in the germ cells, and is not 

 imported into them from the somatic cells of the body. 

 It also gives rise to the question as to what produces 

 dominance of certain characters over others. It is the 



