104 THE VOYAGE OF H.M.S. CHALLENGEE. 



laboratory at Wood's Holl, aud 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 whicli 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 Cluus s Ei-ichtlwidma gracilis^ and -Erich- 

 thoidina a7-mata (fig. 3), and it diflfers 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, aud 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 (PL XII. figs. 1, 2), Faxon's larva and Smith's 

 larva as very young Lysiosquilla, and Claus's Erichthoidina brevisjnnosa and the 

 Challenger Erichthoidina, from St. Vincent (PL XII. fig. 3), as young Gonodactyli, for 

 reasons which wiU be more fuUy 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 dui-ing the ontogenetic development of Lysiosquilla excava- 

 trix, since Faxon's and Smith's larvae have biramous apj)endages 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 Alx>heus, for example, shows 

 that two closely related species may hatch in difi"erent stages, and it is therefore possiljle 

 that one Erichthus may hatch as an Erichthoidina, while another hatches in the Erichthus 

 stage. It is not impossible that some Alima} may hatch as Erichthoidinie, although there 

 is no evidence that this is the case. 



Before I enter upon the general discussion of the Lysioerichthus I will describe 



' Metamorphose tier Squilliden, Taf. i. tig?. 1, 2. 



