1890.] 14:0 [Ryder. 



value or importance in the very highest forms, but which has such an 

 importance in lower ones, may serve a very different purpose in higher 

 types, that is, to find the female element so as to combine with it, which, 

 of course, would be an advantage to the species. In this example, we 

 find an illustration of change of function, or rather the use of an old 

 function in a new way, illustrating also the principle that, any further 

 advantageous step in evolution avails itself of the service of the next pre- 

 ceding one in the order of time, or rather, the latter is apt to thus become 

 a stepping stone to farther progress, as is shown in this instance. 



The parallelism of the Amceba before breaking up into flagellate germs, 

 with a spermatogonium in a higher form is, however, complete, and it is 

 from this basis that further criticisms and suggestions may now proceed. 



Geddes and Thomson, in their suggestive work on sex,* have attempted 

 to identify the evolution of the female germ or ovum with a tendency to 

 develop a leaning towards constructive metabolism or anabolism, while the 

 male germ exhibits the reverse tendency or towards destructive metabolism 

 or katabolism. So far as the directly palpable facts are concerned which 

 lie upon the surface, these conclusions of Geddes and Thomson would 

 seem to be justified. There is apparently nothing in them which con- 

 flicts, at first thought, with the facts of morphology and physiology. Yet, 

 I believe that the prime conclusion of these authors is capable of further 

 analysis, and consequently that it is not as important as it appears to 

 them, nor is it strictly and entirely true in a physiological sense. 



The growth o f an egg we will admit requires constructive metabolism 

 to extend over a longer period than if the germ were male. While it is 

 true that growth represents the expenditure of a certain amount of energy 

 in the form of metabolism, it is by no means clear that the energy of 

 growth required to produce a number of male elements equal in volume 

 to an egg is any greater in the one case than in the other. It may be 

 said that there must necessarily be more cell divisions or karyokineses in 

 the case of a given volume of male elements than in the female, but this 

 goes for nothing in that it cannot be shown that the metabolism or energy 

 expended in building up and segmenting the one is any greater 

 reckoning the additional and usual formation of an egg membrane in the 

 egg (which is wanting in the other element), than in building up the large 

 mass of plasma in the ovum. But in some eggs there is no egg membrane. 

 Even then the process of spermatogenesis is not strictly to be compared 

 with a disruptive metabolism or katabolism ; on the contrary, as an end pro- 

 duct of cytoplasmic activity, the male cell is in the main the highest 

 achievement of constructive metabolism as represented in its preponderant 

 nucleoplasm. The lowest forms of life have apparently a greater capacity 

 for the development of nucleoplasm or chromatin- like substance, than the 

 cells of higher animals, but even there, as in higher forms, there is the 

 best evidence that the cytoplasm is the real agent in the production of the 

 nucleoplasm ; the latter grow T s, as we know, at the expense of the former. 



* " The Evolution of Sex," New York, 1890. 



PROC. AMER. PHILOS. SOC. XXVIII. 132. S. PRINTED MAY 28, 1890. 



