VI 



BRACHYURA LARVAL HISTORY 



- A. 



the Glaucothoe of the Pagurids, resembles a small 

 or Porcellana, the abdomen being still large ami unllexed 

 and furnished with normal 

 pleopods. From this stage 

 the adult structure is soon 

 achieved, though, owing to 

 the continued growth of the 

 Crustacea even after maturity 

 is reached, there is often a 

 slight progressive change in 

 structure, especially in the 

 male, at each successive moult 

 of the individual. The Mega- 

 lopa of Corystes cassivelaunt'S 

 is peculiar in the immense 

 production of the second an- 

 tennae, which act as a re- 

 spiratory tube (Fig. 125). 



The Brachyura must be 

 considered under the follow- 

 ing subdivisions : 



Tribe 1. Dromiacea. 



All authorities are agreed 

 that these 1 are the most 

 primitive of the Brachynra. 

 In them the abdomen is much 



less reduced in both sexes PIG. 125. Later stage (Megalopa) in the de 



velopmeiit of Corysb 

 A. Antenna : A/>. 3rd abdominal segment : 



< ', .uivat chela ; 7 

 (After Gurney.) 



than in other Brachyura; 

 there is a common orbito- 

 antennary fossa, into which 

 eyes and antennae are withdrawn, instead of a separate one mi 

 each side for each organ ; the carapace is often much elongated ;is 

 in the Macrura and Anomura, and a number of other anatomical 

 characters might be mentioned which characterise the iM-unn.i 

 as intermediate between the true Braehyiira and the lo\\er forms. 

 There are, however, two views as t> the relationship <>[' the 

 Dromiacea: Clans held that they proceeded t'nun a (ialalheid 



1 Bouvier, Bull. .SV. Philomath. Paris. (8) viii,, 1896. 



