Protandry and Senescence in Corals. 471 



Remembering the occurrence of a ciliated larva in the Madre- 

 poraria, it is impossible to believe that the colonies of a single 

 species in any area are of the same age, and they certainly are 

 not of the same size, hence have not a like number of polyps. 

 It is consequently necessary to suppose that in an area — owing 

 probably to some change in the physical conditions of their 

 environment — all the corals of some single species have been 

 stimulated to ripen and dehisce their generative products at the 

 same time, the act leading ultimately to their weakening and 

 death. As the colonies in the cases especially examined were 

 female there may be protandry. 



The above explanation is neither complete nor quite satisfac- 

 tory, but it is clearly evident that there is here an entirely different 

 phenomenon to senescence. The only close parallel is that of 

 the larger species of bamboo, in which death follows the act of 

 flowering. Every plant of the commercial species in a district 

 produces its frnctiti cation at the same time and dies. As wide- 

 spread inconvenience commonly results in India, China and 

 Burmah, the circumstance is of common knowledge. There are 

 no definite experiments to show whether the offshoots of bamboos 

 of different ages ab ovo fructify at the same time. It is, however, 

 almost certain that in the country of an intelligent people they 

 must do so, or else they would be largely exported from district 

 to district. The cause in bamboos must be sought in some change 

 of season, and hence there is almost a complete parallel with 

 the above-mentioned colonial corals. The whole phenomenon is 

 obscure, but the circumstances show that there is a phenomenon, 

 which requires — and would almost certainly repay — special in- 

 vestigation 1 . 



The consideration of the above phenomenon arose naturally 

 out of my investigation of the anatomy of Flabellum. It is yet 

 only right to mention that my friend, Mr R. C. Punnett, had 

 more particularly drawn my attention to the question of senes- 

 cence in general. 



1 I would express my thanks to Prof. Marshall Ward for references to the 

 phenomenon of the fructification and death of bamboos. These merely show that 

 there are no definite experiments. For the facts I have relied on Mr Willis' and 

 other information, which I collected in India and Ceylon. 



I have discussed the question of senescence in invertebrates with several 

 zoologists. Mr Bles has mentioned to me the case of an Alcyonium, but un- 

 fortunately no account of it has, so far as I am aware, been published. 



