24 



H. J. Waddington, of Bournemouth, have managed to rear many 

 examples in a state of confinement through a large number of 

 ecdyses. When these experiments are analysed and brought 

 together, it is at once apparent that the successive advances in 

 growth and the periods of the instars are intimately related. The 

 information with reference to the majority of the series has been 

 given in full by Williamson (1903), and it is restated in Table I. 

 For convenience of reference the series are distinguished by the 

 figures and numbers employed by Williamson and by the letters 

 given b}^ Brook. It will at once be plain that in the table I have 

 arranged as well as I was able the respective series with reference 

 to the ecdyses with a view to obtaining mean results, and these 

 were afterwards smoothed. In each case the size is given and the 

 number of days occupied during the instar of that size. By this 

 means the results of season are eliminated, and it is ]oossible by 

 this method to eliminate also the influence of sex. But the sexes 

 exhibit an interesting difference in growth, and in this case the 

 results for each are sho^^m in detail, for the point is important 

 enough to warrant its being emphasised. The smoothed results 

 are expressed in the form of a chart in fig. 6. 



As has been stated already in the previous section, the crab 

 is liberated from the egg in the protozoea condition. The seven 

 pairs of limbs are practically fully developed. The first ecdj^sis 

 yields the first of the so-called zoea stages, but it only differs from 

 its predecessor by having the spines so characteristic of the larvae 

 of this group. During the four stages the remaining limbs appear 

 and grow, but they do not reach a functional state until the ecdysis 

 which produces the megalopa. Each successive larva employs 

 the first two pairs of maxillipeds as natatory organs, the limbs 

 posterior to these are not brought into use. The larval spines 

 do not constitute a zoea, and I venture to submit therefore that 

 all the larval stages preceding the megalopa are or should be styled 

 protozoea. 



The fifth ecdysis gives rise to the megalopa. The dorsal 

 spine in the case of the shore crab is not developed at this stage, 

 and as a rule it is rudimentary in Brachyuran megalopa. The 

 carapace is broad and flattened, thus approaching the adult con- 

 dition, but the abdomen is still directed posteriorly. The limbs 

 are now fully developed and adult-like in appearance, situation 



