president's address. 
127 
first pair of antennae, ami is precisely similar in character to that 
which is formed by the next pair of appendages in Corystes. No 
better case could be given of the striking convergence in the evolution 
of a similar structure, in two animals which are not nearly related 
to one another, from two different parts of the body. In the 
Oxystomatous genus Calappa , an arrangement is present which 
resembles that of the common Cyclometopa of our own shores in 
the formation of a respiratory channel by the apposition of the 
great chelae to the anterior margin of the carapace ; but in this 
case the denticulations which presumably serve to guard the entrance 
to the respiratory passage are formed by the upper margins of the 
“ hands ” of the chelae instead of by the edge of the carapace itself. 
The question of the origin of species is one which has been in 
the forefront of Biological enquiries for the last forty years ; but 
amongst the enormous mass of Zoological writings which have been 
devoted to the description of specific characters there are compara- 
tively few papers in which an attempt is made to elucidate the 
utility of the characters by which species are discriminated. The 
solution of this question is, doubtless, at present beyond our powers 
in the vast majority of cases — and, indeed, it would be going too 
far to assert that specific characters, in general, have any distinct 
utility. But we may be the more grateful to enquirers like 
Mr. Garstang who succeed in finding a clue to some of the riddles 
of Nature, by observations which demonstrate some connexion 
between details which have usually been regarded as trilles useful 
merely in the discrimination of species, and some of the most 
important physiological phenomena in the life of animals. 
The common Starfish ( Asterias rubens) is well known to be one 
of the principal enemies of the Oyster ; and it might have been 
supposed that the modus operandi of so common an animal in 
devouring its prey would have been accurately ascertained long ago. 
The manner in which Starfishes attack Molluscs has, however, 
formed the subject of a paper, by Dr. Schiemenz, published so 
recently as 189G,* in which the older opinions expressed on this 
subject are shown to have been erroneous. The following facts, 
* Translated under the title “How do Starfishes open Oysters?” Journ. 
Mar. Biol. Ass. vol. iv. (Is’.S.), 1805 — 97, p. 266. 
