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 Zoéa 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 Megalopa 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 zoéa 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 neurly 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, bat 
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 Zota and Megulopa stages of Carcinus 
meenas, not, as stated by a misprint, those of Cuncer 
pagqurus. 
