84 
THE VOYAGE OE H.M.S. CHALLENGER. 
the lower Lysiosquillae, in the subgenus Coronis, the larva is not an Alima 
but a Squillerichthus, and if it be true that Squilla and Lysiosquilla represent two 
divergent stems, and that their lower representatives are most closely related, it is 
not at all probable that any species of Lysiosquilla passes through an Alima stage, for 
if it were the case we should be forced to believe that the higher Lysiosquilla have inde- 
pendently acquired the same secondary larval form as the higher Squill se. 
While Claus has given us a very complete history of the Erichthus larva his 
collections did not furnish a connected series of Alima larvae, and although he points out 
the possibility that the very young larva which had been figured by Fritz Muller, 1 as well 
as a very similar one from Messina which he himself figures, 2 are young Alimse, he was 
unable to obtain any of the intermediate stages, and my paper on the larval stages of 
Squilla empusa is the only one in which a tolerably complete series of Alima larvae 
are figured. In this paper I showed that the distinctive characteristics of the larva are 
present at a very early stage of development, and that it is in all essential respects an 
Alima at a time when the last three thoracic somites are not yet marked out, and when 
there are no appendages between the large raptorial limbs of the second thoracic somite 
and the first abdominal appendages. I also pointed out the great probability that this 
larva leaves the egg as an Alima rather than as an Erichthoidina or an Erichthus; a 
probability which is strengthened by the fact that Fritz Muller has figured an egg con- 
taining a larva which is probably in this stage. 
Squilla [Alima) gracilis. — The Challenger collection contains a number of larvae 
which were collected in the tow-net at St. Vincent, and from these I have been able to 
select a series of Alimse, which give a much more complete history of the growth 
and gradual modification of the larva than that which I obtained in 1879. 
This series of larvae, Alima gracilis of Milne-Edwards ( Alima angustata, Dana) is 
shown in PI. IV. figs. 4-6, PI. V. fig. 3, PI. VI. figs. 3-5, and PI. VIII. figs. 4-6. 
Its distinctive or specific characteristics are as follows : — The body is narrow and 
greatly elongated, the exposed hind body making about half the total length as 
measured from the tip of the long slender rostrum. The raptorial claw of the second 
thoracic appendage (PL VIII. fig. 5) is narrow and greatly elongated, and the dactyl us is 
only about half as long as the second joint. 
The telson is remarkably long and narrow, and in the older larvae its length is three 
times its width. It has six large marginal spines (PI. VI. fig. 3 and PL VIII. fig. 6) with 
minute spinules between the submedians, and also between the submedian and the inter- 
mediate. The lateral edge of the greatly elongated narrow flat carapace is armed with 
twelve or thirteen small spines and a larger spine projects from the side of the postero- 
lateral spine near its base. There is a small median dorsal spine on the posterior edge of 
the carapace, which exposes the last three thoracic somites, and is narrowed posteriorly 
1 Archivf. Naturgesch., Jalirg. xxviii. Taf. xiii. fig. 1. 2 Metamorphose der Squilliden, fig. 22 B. 
