Hapalocarcinus, the Gall-forming Crab, etc. 61 
CRYPTOCHIRUS HE ter. 
Cryptochirus is a genus described by Heller in 1872 from the Red 
Sea and associated by Calman with Hapalocarcinus to form the family 
Hapalocarcinide. Heller was not able to impart much information 
about the biology of the crab, but he gives an accurate account of the 
structure, even to the minute oral appendages, accompanied by figures 
which are helpful if hardly adequate according to present standards. 
Semper was the first to supply first-hand observations of the living 
animal which he found inhabiting various Astreid corals in the Philip- 
pines. He discusses the interaction of crab and coral polyps in a 
passage which I will quote in full. 
Semper first states that the influence of the respiratory current of 
Cryptochirus is exerted in quite a different way to that of Hapalocar- 
cinus. This is due to the fact that the former genus only inhabits 
the more massive forms of coral and consequently the cavities in which 
it lives are unlike those in which Hapalocarcinus is found: 
“Here there are no galls, but merely cylindrical or funnel-shaped hollows, 
which are never closed during the lifetime of the crab, so that it certainly 
would be able to quit its position. Nevertheless, it as certainly does not do 
so; but the species I observed living thrust the forepart of their bodies very 
far out of their peculiar ‘cave dwellings,’ so that only their pouches, 7. e., the 
hind part of the body, remained within. The cavity itself exhibits some 
remarkable peculiarities. The bottom of it, on which the pouch rests when 
the creature has completely withdrawn itself into it, displays the radial septa 
of a polyp-cup one above another. They there are perfectly distinct, while the 
side walls of the cylindrical cavity are so completely lined with a thin cal- 
careous crust that nothing can be seen of the perpendicular septa of the polyp- 
cup. From this it is evident that the young crab, or the larva of it, takes up 
its abode in the centre of a cup, and so kills the polyp inhabiting it. A speci- 
men now lying before me, with an incomplete cave-dwelling, shows that the 
crab grows at first at the same rate as the surrounding polyps; for the margin of 
the crab’s hole, which is perfectly cylindrical, is on exactly the same level as 
the neighbouring cups, and its breadth too is exactly the same. The cavity 
is six millimétres long, and the length of the crab found in it exactly corre- 
sponds. In another example, however, the length of the pit is twenty milli- 
métres, while that of the crab belonging to it is not more than seven milli- 
métres, at any rate in the dried state. This proves that the crab ceases to 
grow much sooner than the coral; and this conclusion is strikingly confirmed 
by the fact that the margin of the cylindrical pit is not on the same level as 
that of the surrounding polyp-cups, but much deeper. From the margin of 
the crab’s dwelling, properly so called, there is a funnel that widens to the top, 
and of which the margin, as is shown in the cut (fig. 68), is gradually merged 
in the upper prominences of the coral. The crab living in the funnel thus 
formed was carefully observed by me during a long period of its life, and I was 
enabled to see that it protruded itself far enough out of its hole to be able to 
reach with its outstretched fore-claws almost to the highest portion of the 
funnel. 
“The whole conditions here described allow of no other explanation than 
the following: At first the crab and the coral grow at an equal rate; for, if the 
