60 



Papers from the Department of Marine Biology. 



-d.s. 



This tip is not attenuated, as in most crabs, but is comparatively 

 broad and rounded and bears several small setae. The posterior 

 appendage is much shorter and is inserted in the basal cavity of the 

 anterior appendage. Its apex is broad, not stylet-like, as, for instance, 

 in Cancer. The generally accepted function is that of forcing the 

 spermatozoa into the spermatheca of the female by working up and 

 down in the cavity of the anterior appendage when the copulatory 

 organ is introduced into the vulva of 

 the female, and its piston-like structure 

 would indicate this here. 



I have not observed genital papillae. 



The great length of life in Arthropod 

 spermatozoa is of course well known. 

 The case most often quoted is the bee, 

 where the queen is only once fertilised. 

 In the other Brachyura it is said that 

 the spermatozoa" remain inside the sper- 

 matheca for many months before they 

 fertilise the ova." (I quote from Pear- 

 son.) 



THE EGGS AND LARWL 



The eggs of Hapalocarcinus are quite 

 large in size and heavily yolked. I never 

 observed the larva? hatching, but a great 

 many of the individuals collected bore 

 larvae very nearly ready to be set free. 

 They are then in the zoaea stage, with 

 very distinct frontal, dorsal, and lateral 

 spines, and large paired eyes in the head. 

 All the head appendages are developed 

 and the first two maxillipeds, large bi- 

 ramous structures, in the thorax. The 

 segments of the abdomen are quite distinct and there is a forked 

 telson. It seems, then, that this stage corresponds to the first zoaea 

 stage of Cancer (Pearson) and thus hatching takes place here at a 

 slightly later stage. The great difference between the protozoaea (the 

 hatching stage in Cancer) and the first zoaea is the presence of the 

 frontal and dorsal spines. The protozoaea is apparently omitted from 

 the life-history of Hapalocarcinus. 



The spines of the carapace are less prominent than in Cancer. The 

 dorsal spine is longest. The first antenna is short and stumpy; the 

 second antenna is very short but biramous. The mandible is visible 

 as a not very definite plate. 



FIG. 15. Zosea larva of Hapalocar- 

 cinus. X 90. 



d.s., l.s.,f.s., dorsal, lateral, and frontal 



spines. 



an., first and second antennae. 

 mx., first and second maxillae. 

 mxp., first and second maxillipeds. 



