108 ENTOMOLOGICAL SOCIETY 



ANNUAL ADDRESS OF THE PRESIDENT. 



LONGEVITY IN INSECTS, 



With some unpublished Facts concerning Cicada septendecim. 

 By C. V. RILEY, Ph. D. 



Friends and Fellow -members : 



The question as to the necessity of death, which has been more 

 or less ingeniously discussed in past centuries by philosophers 

 and physicians, has acquired in recent years an added interest 

 from the scientific point of view by virtue of some of the curious 

 theories and experiments of Dr. Brown-Sequard, and of Weis- 

 mann's theory of the immortality of the germ-cell, and the re 

 sultant immortality of the zoospores or unicellular organisms. 

 To be a little more specific as to Weismann's theory, it involves 

 the continuation from the very beginning of life upon our planet 

 of the germ-cell, and in controverting Vines' argument, that it is 

 absurd to say that the immortal substance can be converted 

 into mortal, he takes particular pains to distinguish between what 

 he considers to be the confusion between two distinct ideas, viz., 

 immortality and eternity. The immortality which he refers to 

 of unicellular beings, and the reproductive cells of multicellular 

 beings, is not absolute, but potential. He uses the word " im 

 mortal " to indicate not a substance, but a certain form of motion 

 a force. It is the property of fission, then growth by assimi 

 lation, then fission again, in the physical nature of protoplasm, 

 which he calls immortality. It is, in other words, a purely 

 biologic conception which he distinguishes from the immortality 

 or eternity of non-living or inorganic matter, which is without 

 beginning and without end. The distinction borders upon the 

 metaphysical, but it is w r ell to bear it in mind in discussing 

 Weismann's views. 



In line with this theory of the immortality of the germ-cell, 

 Weismann has devoted a very interesting chapter, in his general 

 work on heredity, to the question, of the duration of life in differ 

 ent species, and quite ingeniously endeavors to show that death 

 is by no means necessary. His premises are substantially these : 

 The duration of life varies, and is by no means fixed in different 

 kinds of organisms, but there is a correlation between longevity, 

 or the duration of life in the individual of any particular species, 

 and the risks which it suns in its struggle for existence, and its 

 fecundity. In other words, the slowest-breeding animals, cceteris 

 paribus, will, on the whole, prove the longest-lived, while the 

 most prolific will be most ephemeral in individual existence. 

 Further, he argues, with the ingenuity that characterizes his 



