BRACHYURI. 157 



haunts, now conceals itself until it hardens. Apprehensive of injuring 

 the new animal by pressure, I have always avoided that test, from my 

 desire of preserving the subject. Nor have I remarked any disposition 

 for concealment, farther than temporary tranquilhty. No exuviation is 

 preceded by sensible enlargement of the animal. Therefore a change 

 of the shell is indispensable. If not equally indurated as the old one, 

 the new shell hardens speedily. Being soft would probably facilitate its 

 escape, on relaxation of the cartilages of that which it quits. 



There is no positive prognostic announcing approaching exuviation, 

 nor any rule for determining its intervals, or its frequency. These de- 

 pend on circumstances peculiar to the individual subject. It is evidently 

 concomitant on increment, therefore commencing at the earliest age. 



I took a minute specimen at Blackness Castle, on September 9. 1814. 

 It cast its shell on the 27th of the same month, and again on the 13 th 

 of October. This new one was replaced by another on the 29 th. There- 

 fore the intervals were about a fortnight. The animal was found dead 

 on December 31st, without farther exuviation. 



I took another young specimen on June 29th of a subsequent year. 

 Its colour was pure gi^een, with three white patches towards the anterior 

 surface of the shell, Plate XXXIV. fig. 1. Similar patches are not un- 

 common on the Cancer iiKsnas ; I have seen specimens half the size of 

 this last marked by them. 



The limbs of that just specified extended 13 lines. It was very ac- 

 tive, and fed voraciously. The shell was cast on Aug-ust 16th, when the 

 white patches of the new one were less conspicuous. Exuviation suc- 

 ceeded again on the 18th of October, and a thu'd time on the 9 th 

 of January, when the shell appeared as in fig. 2, with one patch only. 

 The limbs now expanded about two inches. The animal's rapacity Avas 

 undiminished ; it sprung upon its prey, but could not discover it if at 

 any distance. The shell became gTadually more dingy, and in two 

 months, or ten weeks from the last exuviation, the white patch was 

 totally obliterated. This specimen rejected food on March 20th, and 

 cast its shell, for the fourth time, in the night of the 22d. Its enlarge- 

 ment was now very conspicuous, the Umbs expanding above two inches 



