Sex / by Patrick Geddes ... and J. Arthur Thomson.

  • Patrick Geddes
Date:
[1914]
Catalogue details

Licence: In copyright

Credit: Sex / by Patrick Geddes ... and J. Arthur Thomson. Source: Wellcome Collection.

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    be more or less changed in connection with its new function. Some investigators, such as Tandler and Grosz and Kammerer, have gone the length of maintaining that all sex- characters have arisen from the transforma- tion of species-characters. Just as in the primitive Metazoon body the cells lying next the gametes came by change of function into the service of reproduction, so it may have been that more distant cell-complexes, which had already reached some degree of structural differentiation and subserved other functions, suffered partial or even total loss of their original function, and became auxiliary to reproduction.'' Sex Dimorphism.—In many of the simple backboneless animals, the two sexes are practically identical in appearance, and ex- hibit no definite sex-behaviour. Thus without a microscope it is often impossible to tell a male starfish from a female, or a female from a male sea-urchin. Nor can we see that the one sex is attracted to the other. The fertilisation of the eggs is more or less hap- hazard, but it must be noted that large num- bers of individuals are found living together, and that the males and females become mature about the same time. Both ova and spermatozoa are set adrift in the sea, and as there are thousands of sperms for every ovum the chance of fertilisation is much greater than wrould at first sight appear likely. Moreover, from within a short distance there is a chemotactic M attraction of the sperma- tozoa to the ova (see Fig. 9). It should be noted that animals like sea
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