88 
THE YOYAGE OF H.M.S. CHALLENGER. 
from the telson, although its appendage is represented by a minute bilobed bud. This 
larva therefore has all the appendages of the adult, either functional or represented by 
buds, and all the somites of the hind body except the sixth abdominal. The outer ramus 
of the flagellum of the first antenna is now bilobed, and the flagellum of the second 
antenna is represented by a bud, aud the ocular somite is distinct and movable. The 
rostrum is a little less than half as long as the carapace, and the labrum is still farther 
back. The width of the carapace between the bases of the antero-lateral spines is of 
its width between the bases of the postero-lateral spines, and the carapace with the 
rostrum makes up almost exactly half of the total length (ro°oh)- I n other respects this 
larva closely resembles No. 3. 
Larva No. 5, 17 x ^ mm. long, is shown in PI. IY. fig. 0. The sixth abdominal 
somite is still absent, and its appendages and those of the three last thoracic somites 
rudimentary, although those of the third, fourth, and fifth thoracic somites have assumed 
nearly their final form, and the first antenna has its three-jointed flagella. 
Although actually longer than that of No. 4, the rostrum is now relatively much 
shorter, and only about one-fourth (^) as long as the carapace, and the distance from 
its base to its tip is less than one-half (-Jit) of the distance from its base to the tip of the 
labrum. 
The carapace is still shorter, as compared with the hind body, and with the rostrum, it 
now makes up less than half ( T 4 q 9 o 2 o) of the total length, although its lateral edges are still 
straight, and its triangular shape is still retained. The greatest change is in the length 
of the telson, which is now nearly twice as long as wide. 
Larva No. 6, 42 T 8 X mm. long, is shown in PL VI. fig. 3. It has all the somites 
and appendages of the adult, although the sixth pair of abdominal appendages are 
rudimentary. The carapace is still more elongated, and although the rostrum is actually 
longer than it was in stage 5, it is much shorter both as compared with the total length 
of the body of which it now makes T §^, and also as compared with the carapace, which 
is more than five times (W) as l° n g as the rostrum. One of the most prominent 
characteristics of the fully grown Alima gracilis is the great distance of the mouth from 
the anterior end of the body, and in larva No. 6 the length of the rostrum is little more 
than one-fourth the distance from its base to the tip of the labrum. The carapace 
including the rostrum makes a slightly smaller portion of the total length ( T ^) than at 
stage 5, and its lateral edges are no longer straight but are incurved near their posterior 
ends, so that there is no increase in width in the posterior third of the carapace. 
In the still older larva figured by Claus, this peculiarity is still more marked, and the 
broadest part of the carapace is some distance in front of its posterior margin ; this is 
more emarginatcd in stage 6 than it is in younger larvae, and it crosses the middle of 
the sixth thoracic somite. The telson is still more narrow and elongated, and the sub- 
median spines (PI. VI. fig. 3), which have become more and more closely approxi- 
