DIGESTIVE SYSTEM OF PERIODICAL CICADA. 205 



of life in the animal kingdom. . . . The little males begin to 

 swim soon after hatching, the wheel apparatus and the muscula- 

 ture being vigorous. They seek out the females, as their repro- 

 ductive organs are mature at the moment of hatching. The 

 transparent body, which is devoid of digestive apparatus, swarms 

 with mobile spermatozoa. As soon as the male has seized the 

 female, he discharges the contents of his body. It might be 

 supposed that such an evacuation would cause violent perturba- 

 tion of the system leading to the death of the organism. But the 

 males are able to live for many hours after having accomplished 

 their function, and the period represents a third of their natural 

 duration of life. Moreover, I have isolated males from the fe- 

 males without any prolongation of their life. In one experiment, 

 I isolated two males and placed a third in company with two 

 females. It was the third specimen that lived longest. There 

 can be no doubt but that the death of these male rotifers is 

 natural in the fullest sense. The females, although they are 

 provided with complete digestive organs, do not escape a similar 

 fate. In some Ephemeridae, which supply good cases of natural 

 death, the end comes after a few hours of adult life without any 

 sign of degeneration of the organs. As in others (Chloe) life 

 lasts several days without food ever being taken, it is clear that 

 inanition is not the cause of the swift arrival of death in the first 

 set." 



As will be perceived, these citations from Metchnikoff relate 

 primarily to distinctly different problems. But they afe not 

 without a measure of significance in connection with those under 

 review. One point of importance is the fact that in these widely 

 differing groups of organisms certain very fundamental functions, 

 especially that of reproduction, take place normally during a 

 period of inanition. Granting that the phenomena related of 

 the Rotifers may be somewhat exceptional, and of only incidental 

 significance, certainly those exhibited by the Ephemerids are 

 clearly significant and pertinent, and have much in common with 

 those so conspicuous in the life history of Cicada; thus accentuat- 

 ing the occurrence of kindred phenomena in widely differing 

 organisms. 



