first and second walking legs hanging downwards ready to 

 seize any food particle, draw it up to the body and hand it 

 on to the maxilippedes maxilla,^ and mandibles, where it is 

 crushed and mixed up before passing on to the stomach. 

 The upper and lower lips are in active motion, they cover 

 over the mandibles, thus forming a sort of cavity analogous to 

 the " gastric mill " or grinding stomach of the adult. 



The temporary outer branches of the second and third 

 walking legs function as very active swimming legs in such a 

 way as to direct the body forward. They do not appear to 

 be at all directive. 



The animal, however, is able to turn quickly, even to swim 

 m short somersaults by means of the bending of the long 

 rudder-like hind limbs (third walking legs). The body can 

 also be rotated on its long axis by the movement of these 

 limbs, as they are rather widely directed away from each 

 other posteriorly. 



This stage, like the first, swims rapidly towards the light. 

 After about four days the larvae were observed to be more 

 scattered throughout the tank, often at a distance from the 

 surface. On one or two occasions they were observed to 

 descend to the floor of the tank and rise again. At other 

 times they kept to the margin of the tank, where a number 

 of copepods and small Crustacea occurred, but, although 

 these animals kept clear of the young crawfish, there was no 

 attempt on the part of the latter to seize them. 



About the fifth or sixth day the larvse gradually disappeared. 

 For better observation one was removed from the tank and 

 placed in a bell jar containing clean sea water, which was 

 renewed from time to time. This larvae was very active, 

 swimming about by vigorous movements of its swimming legs, 

 though progression was in no case very rapid. Occasionally, 

 however, there was a rapid turning movement ventrally, 

 apparently for the purpose of seizing floating particles. About 

 the seventh day the young crawfish was observed to be 

 keeping almost exclusively to the bottom of the jar, occa- 

 sionally examining small particles of debris, though a small 

 quantity of boiled yolk of egg placed in the jar was apparently 

 not touched. It was then observed that the animal had so 

 changed its habits that it now avoided the light, instead of 

 seeking it. and it could now be made to move from side to 

 side of the tank, as in the case already mentioned, but in the 

 opposite direction, keeping as far removed as ])ossible from 

 the source of light. The movement, however, was not so 

 marked as in the previous stage. As this fact may prove of 

 importance in elucidating the life history of the animal, the 



