Hapalocarcinus, the Gall-forming Crab, etc. 57 
closest embrace and makes its way very slowly over the surface in 
search of a hole. The legs, though rather weak, are provided with 
sharp claws which it sticks into the ccenosare of the colony. If several 
crabs are contained in the same vessel they come together and fight vig- 
orously (though under natural conditions they can have no opportunity 
of satisfying these proclivities). It is clear that the crab is strongly 
thigmotropic, a property developed in correlation with its secluded life. 
It is first my intention to give an explanatory description of the 
series of females which are illustrated here. As was stated in the 
preliminary description, the crab settles down when it is immature. 
The youngest females, found in galls consisting solely of the chamber 
A, have a carapace length of 1.5 to 1.75 mm. and their sex is hardly 
recognisable. They have a narrow abdomen with no trace of swim- 
merets; there are no reproductive apertures and the genital gland has 
not developed. But there is equally no sign of male characters and a 
perfect gradation exists between these apparently sexless forms and the 
adult female. This youngest female I denote as Stage I. 
In Stage II, though the abdomen is very little broader, rudiments of 
the swimmerets appear and also the female apertures on the sternum 
opposite the third thoracic legs. The carapace length is 2.0 mm. 
In Stage III the abdomen is definitely broader, though only in seg- 
ments 4, 5, and 6. The rudiments of the appendages are rather 
longer and the first pair show indications of bifurcation. The carapace 
length is 2.5 mm. 
In Stage IV all the abdominal segments except the last have shared 
in the increase of breadth. The carapace length is 3 mm. 
Stage V shows further broadening of the abdomen. The carapace 
length is 3.2 mm. 
In Stage VI the abdomen is almost as broad as the carapace. It 
will be seen that the hypertrophy is due to the growth of the last three 
segments. The ovary is well developed in the cephalothorax. The 
carapace length in the specimens figured is 3.5 mm. This appears to 
be the same stage as that described and figured by Calman (l. ¢., pl. 3, 
figs. 29, 30), but he gives the carapace length as 2.6 mm., which is very 
much smaller than that in mine. 
In Stage VII the abdomen is wider than the carapace, the last three 
segments being greatly widened to form a pouch. In nearly all these, 
eggs are found attached to the appendages. The two stages figured 
here show that marked growth takes place even after reproduction 
commences. This may be estimated from the following figures: 
Stage VI a. Stage VI b. 
5.2 mm. 
8.5 mm. to 9.0 mm. 
© Carapnce langthy. « ..2 <i. ois cece 
Ae CUD Ciel ie Omens ey mm ES 
Breadth of carapace..............0- 5.0 mm. 
Greatest total breadth (abdomen)....)  ....... 9.5 mm. to 10.0 mm. 
