THE GAMETES IN PLANTS AND ANIMALS 351 



It is a question of some interest whether the energy expended 

 in the movements of the spermatozoon is derived entirely from its 

 own substance or whether in any case it obtains nutritive material 

 from the fluids in which its movement occurs. It is difficult to 

 understand how some of the more highly specialized forms of 

 animal spermatozoa can contain a sufficient amount of material to 

 furnish energy for their long-continued activity. If the sperma- 

 tozoon does obtain nutrition from the external world after its 

 isolation from the parent body, it may perhaps undergo some 

 degree of senescence even during this period. 



Tests of the susceptibility to cyanide of various developmental 

 stages of the gametes have given uniform results. Thus far I have 

 made susceptibility tests on the female cells of the starfish and sea- 

 urchin, of various marine annelids, and of the fish Tautogolabrus, 

 and upon both female and male cells of the nematode worm Ascaris 

 megalocephala. Ascaris is a particularly favorable form for tests 

 of this sort, first, because ovaries and testes are tubular organs 

 lying in the body cavity and can readily be removed; secondly, 

 because all stages in the development of the male and female 

 gametes can be obtained from a single individual of the proper sex 

 at any time; and, thirdly, because the spermatozoa are non-motile. 

 In both male and female the primitive mother cells in the uppermost 

 or innermost portion of the tubular testis or ovary, where growth 

 and cell division are still occurring, show very high susceptibility 

 like that of embryonic cells; lower down in the tube, where the 

 growth and development of the gametes begin, the susceptibility 

 begins to decrease, and the decrease is progressive as gametic devel- 

 opment proceeds, until in the fully developed gamete the suscepti- 

 bility is exceedingly low. In a potassium cyanide solution, 0.005 

 mol., the primitive female mother cells underwent the death change 

 and disintegrated almost at once, the earlier stages of the growth 

 period in fifteen to thirty minutes, somewhat later stages in one to 

 two hours, while the fully formed eggs showed in most cases no 

 changes until after twenty-four to forty-eight hours in the solution 

 and did not actually disintegrate for several days. Numerous other 

 stages were tested, and in all cases the susceptibility was found to 

 undergo a progressive decrease. The male cells show essentially 



