29 



In fig. 6 the upright lines represent the successive ecdyses, 

 the horizontal lines in step-like succession the instars : the whole 

 lines refer to the female and the dotted lines to the male. The 

 numbers below indicate the numbers of ecdyses, and along the 

 margin at the right to the length in mm. and the weight in gr. 

 The upright lines numbered 0, 1, 2 and 3 refer to the age in years 

 from the time of hatching. The curved lines express the weight 

 in grammes, the upper being that of the male. 



It is quite plain remembering that the chart has been prepared 

 with a close approximation to the observed facts, (1) that the 

 periods of the instars are gradually lengthened, (2) that in the 

 first year there are fifteen ecdyses in the case of the female and 

 seventeen in that of the male. The male thus obtains a start in 

 growth which it does not afterwards lose. Another point inci- 

 dentally evidenced is that although the crab remains during the 

 instar of the same size it is constantly increasing in weight. 



A summary of the facts brought out in the chart is given in 

 Table II. 



TABLE II.— GROWTH OF CARCINUS MAENAS. 



This gives the mean results based on the available material. 

 There is a great deal of variation, due especially to the long spawn- 

 ing and hatching seasons, but it is evident from the experiments 

 in rearing which have been made that the effect of season on 

 growth in the case of the late hatched " " group is compensated 

 for by an acceleration in the " 1 " group. With this in mind we 

 can say with some degree of reason that maturity in the female 

 takes place at about the twenty-first ecdysis. At the time of the 

 ecdysis, when pairing occurs, the ova are in an undeveloped 



