2O4 CHARLES W. HARGITT. 



histories, and that among them are various species of ephemerids. 

 From the early accounts of these insects so graphically described 

 by Swammerdam ("Natural History of Insects," Eng. trans., 

 1758, pp. 103-27), on to the present time, it has been common 

 knowledge that these and other species live as larvae for many 

 months or even two or three years an aquatic life. During this 

 time, they are voracious feeders. Finally, at the time of meta- 

 morphosis, they emerge in enormous swarms during the summer, 

 chiefly at evening, having relatively few hours of adult life, 

 during which mating takes place and soon after the discharge of 

 eggs, the early death of the adults. During this brief period of 

 adult life, they take no food; the digestive system, and especially 

 the mouth organs, being so imperfect as to render them incapable 

 of active function. But like the cicada, these insects have the 

 body tissue loaded abundantly with fat, which, in view of the 

 extremely brief period of activity, can hardly be needed for 

 nutritive purposes, but is doubtless utilized in the main for the 

 rapid growth and perfecting of the generative organs and their 

 products. I have verified these observations repeatedly and I 

 am quite able to confirm what is more formally stated by Metch- 

 nikoff ("The Nature of Man," pp. 271-277). He shows that the 

 rapid death following the act of mating and the discharge of eggs 

 cannot be attributable to this act in itself since many males 

 which have not undergone this action owing to the great excess of 

 male insects yet die as promptly as do others which have partici- 

 pated in the process. He also shows that death cannot be due 

 to the presence of pathogenic organisms since diligent search 

 has failed to reveal their presence; and further that it is not due 

 to phagocytic action, since the organs show no indication what- 

 ever of such invasion. He suggests the probability that such 

 rapid death may be the effect of the early death of the cells of the 

 nervous system, yet gives^no evidence in support of the sugges- 

 tion. In a later work, "The Prolongation of Life," this author 

 emphasizes the significance of natural death in many groups of 

 lower animals and the unique modes of providing against its 

 hazards to the continuity of the species. Among these, he cites 

 observations and experiments upon Rotifera (pp. 113, 118). 

 'The whole course of life from the laying of the eggs until death 

 lasts only about three days and is probably the shortest duration 



