METAMORPHOSES. BRANCHIOPOD A. 415 



(1065.) A subsequent moult gives it the appearance of a perfect 

 Crab ; and then only does the abdomen become folded under the thorax, 

 and the normal form of the species recognizable (fig. 211). 



Fig. 211. 



not 



Metamorphosis of Crab. 



(1066.) Notwithstanding the diversity of form under which the 

 young Crab presents itself at different phases of its growth, examples 

 of which we have here figured, it would seem, from the observations of 

 Mr. C. Spence Bate*, that the progress made towards the mature con- 

 dition is not by any sudden metamorphosis, but by a series of moult- 

 ings similar to those which take place in the adult, and that with each 

 successive moult there is a corresponding degree of progress in its 

 development. But the amount of change at each moult is so little that 

 it gives to the animal but a very small degree of difference in its general 

 appearance ; and it is only by a comparison of the earliest form with 

 the last, and that without any consideration of the intermediate stages 

 in its growth, that the idea of a true metamorphosis in Decapod Crus- 

 tacea has arisen. There are, in fact, six or seven well-marked stages 

 or forms that the growing animal passes through in its progress to 

 maturity ; and each of these is linked to the preceding as well as to 

 that which follows by a succession of changes that are but just ap- 

 preciable. 



(1067.) BRANCHIOPODA. In the Branchiopod Crustacea (so called 

 from this circumstance), the legs used in swimming would appear to be 

 converted into broad-fringed lamellae, so thin that they perform the office 

 of branchiae, and render needless the existence of other instruments of 

 respiration. In Daphnia, for example (fig. 212), a creature common 

 in every stagnant pool, the body is contained, as it were, between two 

 corneous plates, open along their inferior edge. Through this trans- 

 parent envelope the legs may be perceived in constant movement ; and 

 * Phil. Trans. 1848. 



