104 
THE VOYAGE OF H.M.S. CHALLENGEK. 
laboratory at Wood’s Holl, and I have found one specimen at Beaufort, although sickness 
in my family prevented me from studying, and my hope of rearing it from preserving it. 
It died, however, without moulting, like all the young Stomatopod larvae which I have 
tried to rear in captivity. It is essentially like the Erichthoidina, from Honolulu, shown 
in PI. XII. figs. 1, 2, and very similar to Claus’s Erichthoidina gracilis 1 and Erich- 
thoidina armata (fig. 3), and it differs from the Erichthoidina, shown in PI. XII. 
fig. 3, and from Claus’s Erichthoidina brevispinosa, which I hold to be young Gonodactyli, 
in the absence of a spine below the base of the postero-lateral, and in' the greater relative 
distance between this spine and the dorsal spine. 
I shall give reasons for believing that these differences are characteristic of the 
Lysiosquilla Erichthus as distinguished from the Erichthus of Gonodactylus, and as we 
find two corresponding types of Erichthoidina it is natural to believe that one becomes 
converted at last into a Lysiosquilla, and the other into a Gonodactylus. 
I therefore regard Claus’s Erichthoidina gracilis and Erichthoidina armata, the 
Challenger Erichthoidina from Honolulu (PI. XII. figs. 1, 2), Faxon’s larva and Smith’s 
larva as very young Lysiosquillse, and Claus’s Erichthoidina brevispinosa and the 
Challenger Erichthoidina, from St. Vincent (PL XII. fig. 3), as young Gonodactyli, for 
reasons which will be more fully developed in the sequel. If this is true we have a 
most striking corroboration of the correctness of the opinion so ably and ingeniously 
advocated by Claus (Crustaceen System) that the Stomatopod larva without appendages 
upon the last six thoracic somites, in which condition the Alima larva leaves the egg, is 
the phylogenetic descendant of a larva with biramous feet on all these somites, for this 
change must actually occur during the ontogenetic development of Lysiosquilla excava- 
trix, since Faxon’s and Smith’s larvae have biramous appendages on the third, fourth, and 
fifth of these somites, like those on the first and second, although the youngest 
Lysioerichthus, shown in our figure has no traces of them on these somites, or upon 
the sixth, seventh, and eighth. 
The great rarity of Erichthoidina larvae may possibly be due to the fact that 
during this early period of its larval life, the young Stomatopod remains within the 
burrow of its parent, or it may be that the larva does not usually escape from the egg 
until this stage is passed, and that the few specimens which are met with at rare intervals 
are those which have been prematurely hatched. 
The analogy of other Crustacea, the various species of Alpheus, for example, shows 
that two closely related species may hatch in different stages, and it is therefore possible 
that one Erichthus may hatch as an Erichthoidina, while another hatches in the Erichthus 
stage. It is not impossible that some Alimas may hatch as Erichthoidinae, although there 
is no evidence that this is the case. 
Before I enter upon the general discussion of the Lysioerichthus I will describe 
1 Metamorphose der Squilliden, Taf. i. figs. 1, 2. 
