TEMPORARY HERMAPHRODITISM 



103 



This is well exemplified in the case of the ordinary males of 

 Inach'US mauritanicus, of some other Oxyrhynchoi;s crabs, and 

 of the Crayfish Cambarus} During the breeding season the males 

 of /. mauritanicus fall into three chief categories : Small males 

 with swollen chelae (Fig. 73, A), middle-sized males with flattened 

 chelae (B), and large males with enormously swollen chelae (C). 

 On dissecting specimens of the first and third categories it is 

 found that the testes occupy a large part of the thoracic cavity 

 and are full of spermatozoa, while in the middle-sized males 



PiQ. 73. — Inachus mauritanicus, x 1. A, Low male ; B, niiiklle male ; C, high 

 male ; the great chela of the right side is the only appendage represented. 



with female-like chelae the testes appear shrivelled and contain 

 few spermatozoa. These non-breeding crabs are, in fact, under- 

 going a period of active growth and sexual suppression before 

 attaining the final state of development exhibited by the large 

 breeding males. This phenomenon is obviously parallel to the 

 " high and low dimorphism " ^ so common in Lamellicorn beetles, 

 where the males of many species are divided into two chief 

 categories, viz. " low males '' of small size in which the 

 secondary sexual characters are poorly developed, and "high 

 males" of large size in which these characters are propor- 



' Faxon, Ann. May. Nat. Hist. (5), xiii. , 1884, p. 147. 

 - G. Smith, MUth. Zool. Stat. Neapel, xvii., 1905, p. 312. 



