IIEPORT ON THE CRUSTACEA MACRURA. 45 



young animal that very closely resembled the brephalos of the genus Homarus under 



the same condition. I say very closely, but there are some important points of distinc- 

 tion, which may best be appreciated by comparing the following description of the 

 embryo of the present species with that of the young of our common lobster. 



The carapace is circular, and extends over the pereion to the last somite. The 

 rostrum is wanting. The eyes are small, almost minute. The first pair of antennae is 

 two-branched, one ramus being stout, the other slender, and both nearly of one length. 

 The second is also double-branched; one ramus short, the other long; the short ramus 

 represents the permanent scaphocerite of the adult animal, the other the long ftagellum, 

 which is twice the length of that of the anterior pair, and reaches to the posterior extremity 

 of the carapace. The mandibles are present, and are approaching their mature form. 

 The incisive blade has scarcely reached its full proportion, which gives to the synaphipod 

 a large and somewhat pediform appearance. The three succeeding pairs of oral 

 appendages are visible, and approximating to their adult forms. 



The two pairs of gnathopoda are simply pediform, each furnished with a strong 

 basecphysis (or branch sprouting from the basisal joint). The second pair differs from 

 the first in having the basecphysis of the same length as the primary branch, whereas in 

 the first the primary or main branch is shorter than its basecphysis. 



The first pair of pereiopoda has well-developed chelae ; the right and left, being uniform 

 in shape and size, correspond in form with the right or smaller hand in the adult. 



The second pair of pereiopoda is also chelate, but much smaller in size, and corre- 

 sponds closely in form with that of the adult. Neither this nor the preceding pair has 

 an ecphysis attached. The three posterior pairs of pereiopoda are simple, and approxi- 

 mate to the adult character; to these an ecphysis is attached, although the branchial 

 appendages are not present on any of the limbs, unless a small bud-like process attached 

 to the coxa of the second pair of gnathopoda may be so interpreted. 



The first pair of pleopoda appears to be wanting, as in the adult female. The 

 four following pairs are developed as long double-branched appendages surmounting a 

 long stalk. The inner branch, as in the adult female, carries on the margin a small 

 stylamblys, except on the fourth pair. The posterior pair of pleopoda, which ultimately 

 becomes developed into the large side plates of the rhipidura or fan-like tail, differs from 

 the four preceding pairs in having the branches large and the basisal joint short, and 

 in carrying no stylamblys on the margin of the inner branch. 



The telson is long and broad, reaching to beyond the posterior pleopoda for about 

 one-half their length. 



At the period of my examination the various hairs with which the animal is furnished 

 on the several parts of the body were wanting. Evidence of their existence is present, 

 but as they, until the animal has been hatched, and lives freely in the sea for a few 

 hours, invariably remain enclosed within their respective points of attachment, they 



