58 Papers from the Department of Marine Biology. 
As ean be seen from figure 10, the ovary invades the abdomen to a 
great extent. The great size of the abdomen is perhaps best appre- 
ciated in a side view (fig. 9). 
By the time that Stage VII has been reached the gall is almost closed. 
Fertilisation takes place when this stage is reached (see next section). 
After closure of the gall the male is unable to pay further visits, so 
fertilisation must be confined to a brief period and may occur only once. 
But the spermatozoa must retain their vitality for a long time within 
the spermathece, for oviposition proceeds until the gall crab dies, and 
a large number of successive broods are probably produced. 
THE MALE. 
I have mentioned above the fact that the male of Hapalocarcinus 
has remained unknown up till the present, and have quoted Calman’s 
conjecture that the sexes both become mature during a free-living 
phase and that after impregnation the female settles down and forms 
a gall in which she is imprisoned. I was myself at first inclined to 
believe that in Hapalocarcinus we had another example of protandric 
hermaphroditism, like Lysmata seticaudata, described by Spitschakoff.* 
This seemed to be indicated by the male-like appearance of the young- 
est inhabitants of galls with their narrow abdomens. But the absence 
of male apertures and copulatory styles supported the alternative sup- 
position that they were immature females. For some time, then, I 
was unable to find an undoubted male, though I examined as many as 
a hundred galls. But at length, on examining one which was just 
closing, I found it occupied by a female (Stage VI) with her recently 
moulted skin and a much smaller individual of about 1 mm. carapace 
length. This was identified as a male on account of the well-developed 
and typical copulatory styles and a pair of enormous testes full of 
mature spermatozoa, which appeared as opaque white structures in 
the cephalothorax. From this discovery, which I confess was never 
repeated, I conclude that the male is normally very much smaller than 
the adult female and not even so large as the young immature females 
which are found in the least-developed galls; also that he is free-living 
and visits the females within the galls, copulation taking place at a 
period when the gall is still open, but the ovary of the female is already 
well grown. Asin the other Brachyura, so here it only occurs just after 
the female has moulted. Soon after a stock of sperm has thus been 
secured the gall closes up, so that the visits of other males are barred. 
But the female begins to lay eggs and lays apparently brood after 
brood, which develop within the ample shelter of the abdomen until 
they reach the zoza stage. Then the larve are liberated to the exterior 
through the tiny circular outlets of the gall. 
*Zeit. wiss. Zool., Bd. 100, p. 190, 1912. 
