44 Animal Life and Intelligence. 



testis — producing the ova or the sperms. But they are 

 indefinite and not permanent in position. 



In higher forms of life the organs which are set apart 

 for the production of ova or sperms become definite in 

 position and definite in structure. Occasionally, as in the 

 snail, the same organ produces both sperms and ova, but 

 then generally in separate parts of its structure. The two 

 products also ripen at different times. Not infrequently, 

 as in the earthworm, each individual has both testes and 

 ovaries, and thus produces both ova and sperms, but from 

 different organs. The ova of one animal are, however, 

 fertilized by sperms from another. But in the higher 

 invertebrates and vertebrates there is a sex-differentiation 

 among the individuals, the adult males being possessed of 

 testes only and producing sperms, the adult females pos- 

 sessed of ovaries only and producing ova. There are also, 

 in many cases, accessory structures for ensuring that the 

 ova shall be fertilized by sperms, while sexual appetences 

 are developed to further the same end. But however the 

 matter may thus be complicated, the essential feature is 

 the same — the union of a sluggish, passive cell, more or 

 less laden with nutritive matter, with a minute active cell 

 with an hereditary tendency to fission.* 



It is not, however, necessary in all cases that fertiliza- 

 tion of the ovum should take place. The plant-lice, or 

 Aphides of our rose trees, may produce generation after 



* Professor Geddes and Mr. J. Arthur Thomson, in their interesting work 

 on " The Evolution of Sex," regard the ovum in especial, and the female in 

 general, as preponderatingly anabolic (see note, p. 32) ; while the sperm in 

 especial, and the male in general, are on their view preponderatingly katabolic. 

 Regarding, as I do, the food-yolk as a katabolic product, I cannot altogether 

 follow them. The d : fferentiation seems to me to have taken place along diver- 

 gent lines of katabolism. In the ovum, katabolism has given rise to storage 

 producis; in the sperm, to motor activities associated with a tendency to 

 fission. The contrast is not between anabolic and katabolic tendencies, but 

 between storage katabolism and motor katabolism. Nor do I think that " the 

 essentially katabolic male-cell brings to the ovum a supply of characteristic 

 waste products, or katastates, which stimulate the latter to division " (I.e., p. 

 lt'2). I believe that it brings an inherited tendency to fission, and thus 

 reintroduces into the fertilized ovum the tendency w T hich, as ovum, it had 

 renounced in favour of storage katabohsm. 



