POST-LARVAL STAGES OF JASUS LALANDII. 109 



The first pereiopod is 5*23 mm. in length — that is, the length o£ the body 

 '(3*8) is contained in it 1"37 times, Avhereas the length of the body in the 

 preceding stage is contained in the length of its first pereiopod 1"7 times. 

 The length of this appendage is therefore relatively less than in the preceding- 

 stages. This relative shortening has taken place least of all in the first and 

 last segments, next in the third and fourth, then in the second, the greatest 

 relative shortening being in the fifth segment. 



The second pereiopod is very similar to the first, but is somewhat longer 

 by about half a millimetre. The increase is in the fifth segment^ which is 

 •45 mm. longer than in the last appendage. 



The third pereiopod differs little from the two preceding. There is now a 

 setose exopodite, considerably shorter, however, than those of the preceding 

 pereiopods. 



The fourth pereiopod consists of a short unsegmented limb 1'28 mm. in 

 length ; about '4 mm. from its base there is a short exopodite '22 mm. 

 in length. 



A great development of the digestive gland has taken place. The posterior 

 lobes have not changed much, and are still quite separate from the main 

 mass. The anterior lobes can also be readily made out^ but the lateral lobes 

 are much enlarged and have lost their trilobed condition. 



Phyllosoma of 24 mm. 



The cephalic shield has increased in relative size, being about 16 mm. 

 broad and the same in length, or 1^ times in the total length of the body. 

 It extends backwards over the thorax to about a line joining the anterior 

 points of the insertion of the first pair of walking-legs. 



There is no trace of spines on the dorsal side of the shield. Anteriorly 

 it is produced as a prominence, on which the base of the eye-stalk is 

 inserted. 



The antennxdes are three-jointed and have two terminal flagella, the outer 

 extending 1 mm. beyond the peduncle of the antennae. 



The antennce are about twice the diameter of the antennules. There are 

 three well-marked segments, the first of which is shorter than the second, 

 which is equal to the third ; the last is terminated by a very strong spine on 

 the inner side. Just beyond it is a joint in the flagellum^ the bi-eaking joint 

 in the adult, and the segments of the flagellum begin to show faintly at some 

 distance from it. The first section of the appendage, fused to the body and 

 containing the antennal gland, shows no trace of demarcation from the head 

 region. There is no trace of an exopodite. The upper lip, mandibles, and 

 first maxillce form a mass round the mouth, now smaller in proportion to the 

 head region, being about 9 times in the breadth of the shield. 



