198 



INVERTEBRATA 



CHAP. 



By three successive moults the length of the posterior part of the 

 body is increased, and at each moult a new pair of stump -like 



FIG. 145. Three stages in the further develop- 

 ment of the. larva of Cyclops. (After Clans.) 



A, stage in which gnathites have appeared. B, 

 stage in which rudiments of thoracic legs have ap- 

 peared. C, stage after critical moult. Letters as in 

 previous figure. In addition, caml.f, caudal fork ; ex, 

 excretory matter in the walls of the alimentary canal ; 

 7Mi, first maxilla; m&, second maxilla; mxp, maxilli- 

 pede ; tlil-*, first, second, third, and fourth thoracic 

 appendages respectively ; oc, eye. 



rudiments of thoracic feet appears. 

 Then comes a critical moult, at 

 which the larva changes its whole 

 appearance and practically attains 

 the adult form (Fig. 145, C). The 

 breadth is diminished and the length 

 increased ; the first appendage has 

 become many jointed and approxi- 

 mates in shape to the first antenna 

 of the adult. The second appendage 

 loses its masticatory hook and its 

 endopodite, and has now become 



shorter than the first : it becomes the second antenna of the adult. 



The third appendage loses everything but the basal joint, and so is 



