DEVELOPMENT. 93 



of cases, by fwn-scxual methods of reproduction, which will 

 be subsequently pointed out. The incapacity for sexual 

 procreation displayed by young animals is in accordance 

 with an important and well-established law, the exposition 

 of which we owe to Dr W. B. Carpenter, that the process of 

 generation is one opposed to that of nutrition, and, a fortiori, 

 hostile to growth and development. The nutritive processes 

 of the young animal are much more active than those of the 

 adult, and so long as this remains the case, the generative 

 functions remain in abeyance. It is not till the organism 

 has reached the point of nutritional equilibrium, that it be- 

 comes capable of exercising the function of reproduction in 

 its highest and most genuine phase. 



Von Baer's Law of Development. — As the study of 

 living beings in their adult condition shows us that the dif- 

 ferences between those which are constructed upon the same 

 morphological type depend upon the degree to which special- 

 isation of function is carried, so the study of development 

 teaches us that the changes undergone by any animal in 

 passing from the embryonic to the mature condition are due 

 to the same cause. All the members of any given sub-king- 

 dom, when examined in their earliest embryonic condition, are 

 found to present the same fundamental characters. As de- 

 velopment proceeds, however, they diverge from one another 

 with greater or less rapidity, until the adults ultimately be- 

 come more or less different, the range of possible modifica- 

 tion being apparently almost illimitable. The differences 

 are due to the different degrees of specialisation of function 

 necessary to perfect the adult, and therefore, as Von Baer 

 put it, the progress of da'eloptncut is from the general to the 

 special. 



It is upon a misconception of the true import of this law 

 that the theory arose, that every animal in its development 

 passed through a series of stages, in which it resembles, in 

 turn, the different inferior members of the animal scale. 

 With regard to man, standing at the top of the whole 



