METAMORPHOSES. 19 



being a little longer than the inner one. On the lower 

 segments in both rami of all the limbs, there is a single 

 spine. In all the limbs, the obliquely truncated summit 

 of the terminal segment of the inner ramus bears three 

 very long, beautifully plumose spines : in the first pair, 

 the summit of the outer ramus bears four, and in the 

 five succeeding pair, six similar spines. This difference, 

 small as it is, is interesting, as recalling the much greater 

 difference between the first and succeeding pairs, in the 

 first and second stage of development. The terminal seg- 

 ments of all the rami, bearing the long plumose spines, 

 are directed backwards. The limbs and thorax are well 

 furnished with striated muscles. The animal, according 

 to Mr. King, swims with great rapidity, back downwards. 

 The limbs can be withdrawn within the carapace. 



Abdomen and Caudal Appendages. — The abdomen is 

 small, and its structure might easily be overlooked with- 

 out careful dissection of the different parts : it consists of 

 three segments ; the first can be seen to be distinct from 

 the last thoracic segment, bearing the sixth pair of limbs, 

 only from the fold of the epimeral element, and from its 

 difference in shape; the second segment is very short, 

 but quite distinct ; the third is four or five times as long 

 as the second, and bears at the end two little appendages, 

 each consisting of two segments, the lower one with a 

 single spine, and the upper one with three, very long, 

 plumose spines, like those on the rami of the thoracic 

 limbs. The abdomen contains only the rectum and two 

 delicate muscles running into the two appendages, be- 

 tween the bases of which the anus is seated. 



Internal Viscera. — Within the body, in front of the 

 mouth, it was easy to find the stomach (with two pear- 

 shaped cseca at the upper end), running first anteriorly, 

 and then curving back and reaching the anus by a long 

 rectum, difficult to be followed : it appeared, however, 

 to me, that this stomach had more relation to the young 

 Cirripede, of which every part could now generally be 

 traced, than to the larva, with its closed and rudimentary 



