WATER-BABIES 61 



very conspicuous, but at an earlier period it has much 

 longer spines on the carapace, and as yet no rudiments 

 of the legs of the trunk or pleon. After many months 

 they attain the final Zoea stage, in which the terminal 

 segment of the pleon is very broad, and divided nearly 

 to the base by a broad sinus, formed by long spiniform 

 diverging processes, at the base of which the sinus is 

 armed with six to eight spines on each side. Shortly 

 before the change into the second or Meyalopa form, ' they 

 were not quite so active as previously, but still continued 

 to swim about until they appeared to be seized by violent 

 convulsions, and after a moment began to wriggle rapidly 

 out of the old zoea skin, and at once appeared in the full 

 megalops form. The new integument seems to stiffen at 

 once, for in a very few moments after freeing itself from 

 the old skin the new megalops was swimming about as 

 actively as the oldest individuals. In this megalops stage 

 the animal begins to resemble the adult. The five pairs 

 of cephalothoracic legs are much like those of the adult, 

 and the mouth-organs have assumed nearly their final 

 form. The eyes, however, are still enormous in size, the 

 carapace is elongated and has a slender rostrum and a 

 long spine projecting from the cardiac region far over the 

 posterior border, and the abdomen is carried extended, 

 and is furnished with powerful swimming legs as in the 

 Macroura.' Professor Smith observed a few instances of 

 the change from the megalops or Megalopa stage to the 

 young crab. ' The little crab worked himself out of the 

 megalops skin quite slowly. For a short time after their 

 appearance the young crabs were soft and inactive, but 

 the integument very soon stiffened, and in the course of 

 two or three hours they acquired all the pugnacity of the 

 adult. They swam about with ease, and were constantly 

 attacking each other and their companions in the earlier 

 stages.' 



Professor Smith has remarked that in ' The Crayfish,' 

 fig. 74 represents the Zoea and Megalopa stages of Carcinus 

 mcenas, not, as stated by a misprint, those of Cancer 

 pagurus. 



