CONTRIBUTIONS TO MARINE BIONOMICS. 227 
nexion there would be a risk of the animals being occasionally buried 
to a dangerous depth by the accumulation of sand above them. Mr. 
W. Thompson’s statement that the antenne in very small specimens are 
much longer in proportion to the carapace than in the adult harmonizes 
well with this hypothesis, as to ensure safety the young would have to 
burrow to a greater depth compared with the adults than would be pro- 
portionate to their size.” Mr. Hunt was not aware of Gosse’s view 
when he framed the above theory; but, subsequently, in a footnote 
to his paper, he referred to Gosse’s theory as identical with his own. 
The two are, however, essentially distinct, if I correctly understand Mr. 
Hunt’s language. According to Gosse’s view, the function of the 
antennz is to produce a tube subservient to respiration; according 
to Mr. Hunt’s, the function of the elongated antennz is essentially 
sensory, viz., to enable the buried crab to determine the depth to which 
it burrows. The “danger” to which Mr. Hunt refers is clearly not the 
danger of suffocation, but the danger of dislodgment from the sand by 
wave-currents. The arenicolous habits of Corystes are adduced by Mr. 
Hunt to illustrate one of the various methods adopted by marine 
animals for resisting wave currents—a view which, in the case of 
Corystes, 1 am unable to accept, partly on account of the normally deep 
water habitat of the crab, and partly on account of evidence given 
below which tends to shew that the burrowing habits of Corystes are 
adopted primarily for concealment. 
IV. New OBSERVATIONS AND EXPERIMENTS. 
(a) Burrowing Habits. A number of living Corystes cassivelaunus 
were placed in a series of vessels containing sand of different degrees of 
coarseness, and it was soon noticeable that these crabs readily burrow 
in fine sand, but find great difficulty in penetrating very coarse sand or 
gravel composed of small pebbles. Moreover, a crab that has obstinately 
declined for several hours to burrow in coarse, gravelly sand, will imme- 
diately bury itself, if placed in an aquarium of fine sand. In all cases 
the process of burrowing is effected exclusively by means of the 
thoracic legs. The crab sits upright on the surface of the sand; the 
elongated, talon-like claws of the four hindmost pairs of legs dig deeply 
into the sand ; the body of the crab is thus forcibly pulled downwards 
by the grip of the legs, and the displaced sand is forced upwards on the 
ventral side of the body by the successive diggings and scoopings of the 
legs ; the slender chelate arms of the first thoracic pair assist in the 
process of excavation by thrusting outwards the sand which accumulates 
round the buccal region of the descending crab. This action at the same 
time, no doubt, loosens the sand in the immediate neighbourhood, and 
