170 



While working at the Biological Station, Heligoland, 

 I was able to examine the early larval stages of Cancer. 

 [ was fortunate enough to obtain berried crabs on which 

 the embryos were ready for hatching. The process of 

 hatching lasted several hours, and during this time the crab 

 assisted by moving its abdomen backwards and forwards. 

 The last walking legs were also used for the purpose 

 of detaching the larvae from the pleopods. Unfortunately, 

 I was not successful in keeping the larvae alive longer 

 than the first zoea stage. 



I give below a summary of the characters of the 

 larval stages of the Brachyura in general. I have 

 utilised the results of other investigators,* and have also 

 added my own observations. The larval stages may be 

 divided into Protozoea, Zoea (four kinds) and Megalopa. 



Protozoea (PI. XIII, figs. 83, 84). Hatching takes 

 place at this stage, which is of very short duration. 

 There are no frontal or dorsal spines present. The lateral 

 spines (sp. I .) are present one on each side of the cephalo- 

 thoracic shield. The large paired eyes are present in the 

 head. The abdomen is well defined, but only five somites 

 and the telson can be distinguished. The sixth somite 

 is at this stage fused with the telson. The telson is 

 forked, and each branch bears strong spines (fig. 84). 

 All the cephalic and the first two pairs of thoracic limbs 

 are present. The antennule is blunt and consists of two 

 segments, of which the distal is the larger. The antenna 

 consists of a broad basal joint, from which is given off a 

 short pointed process. The mandible is a small rounded 

 outgrowth. The first and second pairs of maxillae are 



* Williamson, H. C. " On the Larval and Early Stages and Rate 

 of Growth of the Shore Crah (Carcinus mamas)," Tiventy-first Annual 

 Report, Fishery Board for Scotland, p. 136. 



Korschelt and Heider. Text Book of Embryoloqy (Invertebrates, 

 Part II). ' 



