A HISTORY OF KENT 



this bountiful supply. Inquiries with a view to restrictive legislation 

 have led to many valuable reports, those of recent years by Wilson, 

 Meek, Cunningham and Williamson usefully combining scientific with 

 economic conclusions. Only one or two points out of many can be 

 considered here. The process called ecdysis or exuviation is repeated 

 probably several times in the life of every crustacean that reaches 

 maturity. Many a schoolboy, preparing for a swim, instead of sedately 

 taking off his garments one by one, will slip out of them all at one 

 cast. A crab with the growing pains improves upon this. It slips out 

 of its skin. It comes so clean and clear away from the skin of its teeth 

 and the teeth of its skin that the slough is a complete model of the 

 animal with carapace, limbs, jaws, feathered hairs, delicate spines, or 

 whatever else may be the appropriate furniture. Having become too 

 stout for its unyielding harness the crab bursts it, obviously for the sake 

 of getting a chance to expand in a new and still flexible vest. But such 

 of the Decapoda as have inflated claws, strongly encrusted and narrow 

 at the joints, can find no easy task in withdrawing their arms from these 

 natural sleeves. The procedure which they have inherited and cannot 

 dispense with is no longer very well suited to the accoutrement with 

 which in process of time they have become equipped. But besides 

 being essential to growth, the casting of the shell is also of service in the 

 pairing of crabs. It does not occur simultaneously in the two sexes. 

 The male Cancer pagurus is still securely armoured while his consort is 

 in the soft helpless state which follows exuviation, and under these 

 circumstances is repeatedly found keeping watch and ward over her. 

 Some naturalists, observing the husbands in this apparently chivalrous 

 attitude, looked upon it as probably ' a pretty trait of cancerine character, 

 and one not unworthy of their acute instinct and sagacity in other 

 respects.' ' There is however a somewhat less sentimental explanation 

 available. There is reason to think that only while the skin of his 

 partner is still pliable can the male find the auspicious time for intro- 

 ducing into the spermatheca the fertilizing elements.'' Between the two 

 sexes there are several differential characters. By one of them, according 

 to Dr. Williamson, ' it is possible to distinguish the sex of a crab when 

 it is little more than a quarter of an inch in breadth.'^ This difference 

 lies in the circumstance that the infolded abdomen or pleon of the 

 female has four pairs of swimmerets, whereas the first and second paired 

 appendages of the male pleon are modified into organs for conveying the 

 spermatophores into the spermatheca. While both sexes are still small, 

 the narrow pleon of the male is contrasted witb the broad one of the 

 female, and later on the male is further distinguished by his more mas- 

 sive claws and by having the crenulated edge of his carapace broader 

 and somewhat upturned. That the genital openings belong to the 

 ultimate thoracic segment in the male but to the antepenultimate in the 



1 White, Popular History of British Crustacea, p. 39 (1857), quotation from Gosse. 

 ' Fishery Board for Scotland, l8iA Annual Report, pt. 3, 82. 

 3 Loc. cit. p. 99. 



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