104 Part III. — Eighteenth Annual Report 



Table VII. — Proportion of Males to Females among Hard and Soft Crabs. 





Dunbar. 



Crail. 



D unbar and Crail. 





Males. 



F'males. 



Number 

 of Males 

 to 100 

 Females. 



Males. 



F'males. 



Number 

 of Males 

 to 100 

 Females. 



Males. 



F'males. 



Number 

 of Males 

 to 100 

 Females. 



Beach Crabs . 



1154 



1178 



97-9 















Creel f Undersized 



909 



623 



146 



188 



202 



93 



1097 



825 



133 



Crabs -\Gauge Size 



2916 



2774 



105 



2644 



1814 



146 



5560 



4588 



121 



Exuviation, Casting, Shedding. 



The crab, as is well known, can only increase in size by getting rid of 

 its hard integument. This process, which is known as " casting " or 

 " shedding," has been described for the edible crab by Jonathan Couch,* 

 and for the lobster by Herrick.t I am indebted for the Report con- 

 taining Couch's paper to the kindness of Edward Kitto, Esq., Falmouth. 

 Within a short time after casting the shell increases in size, and after 

 calcification the only increase which takes place in the animal is in its 

 weight. The histological description of this process in a number of 

 decapod Crustacea has been fully described by Vitzou.J This part of 

 the subject it is not proposed to enter upon at present. 



When a crab is preparing to cast, the dermal areolar tissue (tissu 

 conjonctif of Vitzou) is permeated with a viscid fluid, which, in addition 

 to rendering this layer tense and elastic, gives it a characteristic amber 

 colour. This layer extends all over the body, and is especially thick at 

 the edge of the dorsum. When the crab casts, the shell opens along the 

 suture between the epimera and the inturned edge of the carapace ; 

 two of the layers of the new shell (viz., the cuticle and the pigment 

 layer) are already formed, and a slight calcification has taken place 

 round the periphery of the carapace. During the process of casting the 

 crab lies hid, and in the case of an adult female it is at this time 

 fertilised. It apparently leaves its retreat only after a certain amount 

 of calcification has taken place ; it then seeks actively for food. Crabs 

 in this condition are caught in great numbers in the crab-creels during 

 autumn and winter. A considerable amount of attention was paid by the 

 Royal Commission of 1876 to the destruction of the soft crabs which 

 takes place during these seasons of the year. Buckland§ says . — "A 

 soft crab may mean two different things. Firstly, it may mean a crab 

 which has just cast its shell and is soft to the touch like putty ; or it 

 may mean a crab whose shell is very brittle like thin glass, in which 

 condition it is called ' soft crab,' 'caster,' light-footed crab/ 'light crab,' 

 'white-bellied crab,' ' peelert,' 'puller,' ' metick,' ' seeding -crab,' 

 'watery crab,' ' white crab,' 'ripe crab,' ' pale crab,' 'sheer' or 'sick 

 crab.' I myself prefer to call it ' glass crab.' These crabs have not 

 recovered their condition after casting ; they are, in fact, ' kelt ' crabs. 

 I have dissected several, and find that they contain very little else but 

 the stomach, liver, lungs, and other viscera, but always a great deal of 



* "On the Process of Exuviation and Growth in Crabs and Lobsters, etc." Eleventh 

 Annual Report of the Royal Cornwall Polytechnic Society, 1843, Falmouth, 

 f Op. cit., p. 84. 



% " Recherches sur la Structure et la Formation des Teguments chez les Crustaces 

 Decapodes." Archives cle Zoologie Exph'imentale et Generate, T. 10, 1882, Paris. 

 § Op. cit., p. 12. 



