22 
RESPIRATION IN SAND-BURROWING CRABS. 
II. 
ABSTRACT OF AN ADDRESS ON 
RESPIRATION IN SAND-BURROWING CRABS 
Delivered 2jlh September, 1904. 
At the September meeting of the Society, the President 
(Mr. W. Garstang, M.A.) described a number of aquarium 
experiments which he had made with Crabs of various species 
at the Plymouth Laboratory, in order to discover the means 
by which burrowing forms carry on the process of respiration 
when submerged in sand. 
The gills being enclosed in a pair of chambers, the narrow 
entrances to which are situated on the under-side of the body, 
it had not previously been clear how the Crabs could draw up 
a sufficient supply of water, free from particles of sand and 
mud, when their bodies were immersed below the sea-bed. 
It was found experimentally that in many cases the claws, 
together with the marginal spines of the shell, played an 
important role in this connection. In the common Shore-crab, 
and in all the Swimming Crabs ( Portunidce ), the legs bearing 
the claws are well known to be so shaped that when flexed 
against the Crab’s breast they follow its curvature and fit 
it exactly. The narrow gap between them and the breast of 
the Crab is roofed over by the row of marginal spines on the 
shell, the number of which varies in different species, but the 
extent of which always corresponds with the length of the 
gap between breast and claw. The row of spines and the 
notches between them were found to serve the purpose of a 
sieve or grating, while the water for respiration did not pass 
directly into the gill-chamber through the ventral aperture, 
but was sucked downwards through this sieve, being guided 
