16 
THE VOYAGE OF H.M.S. CHALLENGER. 
and that two allied species of adults may have originated in the same manner from a 
common type, while their larvae have remained alike. 
Still, after all these allowances, it still remains true that, inasmuch as the larvae of 
two closely related species are themselves more closely related by blood than the larvae of 
more widely separated species, their bodily structure must exhibit a record of this relation- 
ship which can be discovered by study and comparison, and which will agree to some 
extent with the record presented by the organisation of the adults ; the degree of 
agreement depending upon the completeness of the two records and the correctness of 
our interpretation. 
What then is the natural or phylogenetic classification of the Erichthidae or 
Stomatopod larvae when they are studied by themselves and treated as adult animals ? 
The genera of Erichthidae which have been recognised by the systematists are 
Ericlithoidina , Erichthus, Squillerichthus, and Alima, and of these four the first, 
Erichtlioidina, is simply a young Erichthus, and the third, Squillerichthus, a fully grown 
larva of the Erichthus type, so that the genera become reduced to two, Erichthus and 
Alima. Of these two genera, one, Alima, is much more sharply defined than the other, 
Erichthus, which contains a number of divergent types which admit of definition. 
Three of these types are represented in the collection by numerous species, and are well 
known. As it will be convenient to have names for them I shall use names which 
indicate the adult genera or subgenera to which they are to be referred. 
The Gonerichthus type, which Claus correctly refers to the genus Gonodactylus, 1 for 
reasons which receive added weight from the study of the Challenger specimens, is shown 
in PL XY. fig. 6. 
The Pseuderichthus type, which Claus has given very conclusive reasons 2 for 
regarding as the young of Pseudo squilla, is shown in PI. XII. fig. 6. 
The Lysioerichthus (PI. XI. figs. 1-5), which Claus erroneously regards as the 
young of Squilla , 3 is, as I shall show, the young of Lysiosquilla. These three groups, 
together with Alima (PL I. figs. 4, 5), which Claus regards as the young of 
Lysiosquilla , 4 but which, as I shall show, is confined to the genus Squilla and diagnostic 
of this genus, include nearly all the Stomatopod larvae, although there are a few larvae 
which have a more isolated position, such as the one shown in Claus’s fig. 14, which I 
shall designate as Erichthalima, and others which are intermediate between the three 
Erichthus types. The statement on p. 610 and footnote in Claus’s Grundziige der 
Zoologie, that he has shown from the study of alcoholic specimens that Alima is the 
young of Squilla will seem to conflict with my own statement that he regards Alima as 
a young Lysiosquilla , but a reference to pp. 132, 133, 134, 135, 136, 138, and 154 of his 
Monograph will show that he refers a number of Erichthus larvse to the genus Squilla, 
1 Metamorphose (ler Squilliden, pp. 138 and 139. 2 Metamorphose der Squilliden, pp. 140-146. 
3 Metamorphose der Squilliden, pp. 132, 133, 134, 135, 136, and 138. 4 Metamorphose der Squilliden, p. 154. 
