600 APPENDIX A. 



with the size of the cerebrum. As in all cases co-ordination of 

 actions constitutes the life, or, what is the same thing, the ability 

 to maintain life ; and as throughout the animal kingdom this co- 

 ordination, under all its forms, is effected by nervous agents of 

 some kind or other ; and as each of these nervous agents per- 

 forms but one function ; it follows that in proportion to the 

 number of the actions co-ordinated must be the number of 

 nervous agents. Hence the nervous system becomes the universal 

 measure of the degree of co-ordination of actions; that is, of the 

 life, or ability to maintain life. And if the nervous system varies 

 directly as the ability to maintain life, it must vary inversely as 

 the ability to multiply.* 



And here, assuming the constitution of the sperm-cell above 

 inferred to be the true one, we see how the obverse a priori prin- 

 ciple is fulfilled. Where, as amongst the lowest organisms, bulk 

 is expressive of life, the antagonism of individuation and re- 

 production was broadly exhibited in the fact that the making of 

 two or more new individuals was the wnmaking of the original 

 individual. And now, amongst the higher organisms, where bulk 

 is no longer the measure of life, we see that this antagonism is 

 between the neural elements thrown off, and that internal neural 

 mass whose bulk is the measure of life. The production of co- 

 ordinating cells must be at the expense of the co-ordinating appa- 

 ratus ; and the aggregation of the co-ordinating apparatus must 

 be at the expense of co-ordinating cells. How the antagonism 

 affects the female economy is not so clear. Possibly the provision 

 required to be made for supplying nervous as well as other nutri- 

 ment to the embryo, involves an arrest in the development of the 

 nervous system ; and if so, probably this arrest takes place early 

 in proportion as the number of the coming offspring makes the 

 required provision great : or rather, to put the facts in their right 

 sequence, an early arrest renders the production of a numerous 

 offspring possible. 



14. The law which we have thus traced throughout the ani- 



* That the size of the nervous system is the measure of the ability to 

 maintain life, is a proposition that must, however, be taken with some 

 qualifications. The ratio between the amounts of gray and white matter 

 present in each case is probably a circumstance of moment. Moreover, the 

 temperature of the blood may have a modifying influence ; seeing that small 

 nervous centres exposed to rapid oxidation will be equivalent to larger ones 

 more slowly oxidized. Indeed, we see amongst mankind, that though, in 

 the main, size of brain determines mental power, yet temperament exercises 

 some control. There is reason to think, too, that certain kinds of nervous 

 action involve greater consumption of nervous tissue than others ; and this 

 will somewhat complicate the comparisons. Nevertheless, these admissions 

 do not affect the generalization as a whole, but merely prepare us to meet 

 with minor irregularities. 



