54 THE DURATION OF LIFE. 



beyond the summer at the beginning- of which they founded 

 colonies. At the first appearance of frost, the young fertilized 

 females seek out winter quarters ; the males which never survive 

 the winter, do not take this course, but perish in October. The 

 parthenogenetic females, which remain in the nest during the 

 nuptial flight, also perish. 



The males of Polities gallica do not live longer than three 

 months from July to the beginning of October ; the partheno- 

 genetic females live a fortnight longer at the outside from the 

 middle of June to October, but the later generations have a shorter 

 life. The sexual females alone live for about a year, including the 

 winter sleep. 



A similar course of events takes place in the genus Ve&pa. In 

 both these genera the possibility of reproduction is not restricted to 

 a single female in the nest, but is shared by a number of females. 

 In the genus Apis alone is the division of labour complete, so that 

 only a single female (the queen) is at any one time capable of re- 

 production, a power which differentiates it from the sterile workers. 



NOTE 4. THE DURATION OF LIFE OF THE LOWER MARINE ANIMALS. 



I have only met with one definite statement in the literature of 

 this part of the subject. It concerns a sea anemone, which is a 

 solitary and not a colonial form. The English zoologist Dalyell, in 

 August, 1838, removed an Actinia mesembryanthemum from the sea 

 and placed it in an aquarium *. It was a very fine individual, 

 although it had not quite attained the largest size ; and it must 

 have been at least seven years old, as proved by comparison with 

 other individuals reared from the egg. In the year 1848, it was 

 about thirty years old, and in the twenty years during which it had 

 been in captivity it had produced 334 young Actiniae. Prof. 

 Dohrn, of Naples, tells me that this Actinia is still living to-day, 

 and is shown as a curiosity to those who visit the Botanical Gardens 

 in Edinburgh. It is now (1882) at least sixty-one years old 2 . 



1 Dalyell, ' Rare and Remarkable Animals of Scotland,' vol. ii. p. 203 ; London, 

 1848. 



[ a Mr. J. S. Haldane has kindly obtained details of the death of the sea anemone 

 referred to by the author. It died, by a natural death, on August 4, 1887, after 

 having appeared to become gradually weaker for some months previous to this date. 

 It had lived ever since 1828 in the same small glass jar in which it wae placed by 

 Sir John Dalyell. It must have been at least 66 years old when it died. E.B.P.] 



