10 THE VOYAGE OF H.M.S. CHALLENGER. 



aud 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 Erichthidge 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 

 Erichilioidina, Erichthiis, Squillerichthus, and Alima, and of these four the first, 

 Erichthoidina, is simply a young Erichthus, and the third, Squillerichthus, a fully grown 

 larva of the Erichthus ty^e, 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 Glaus correctly refers to the genus Gonodactylus,^ for 

 reasons which receive added weight from the study of the Challenger specimens, is shown 

 in PI. XV. fig. 6. 



The P sender ichthus type, which Glaus has given very conclusive reasons^ for 

 regarding as the young of Pseud osquilla, is shown in PI. XII. fig. 6. 



The Lysioer ichthus (PL XI. figs. 1-5), which Glaus erroneously regards as the 

 young of Squilla,^ is, as I shall show, the young of Lysiosquilla. These three groups, 

 together with Alima (PI. I. figs. 4, 5), which Glaus regards as the young of 

 Lysiosquilla,'^ but which, as I shall show, is confined to the genus Squilla and diagnostic 

 of this genus, include nearly all the Stomatopod larvas, although there are a few larvae 

 which have a more isolated position, such as the one shown in Glaus'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 Glaus's Gruudziige 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 larvae to the genus Squilla, 



1 Metamorpliose der Squilliden, pp. 138 and 139. 2 Metamorphose der Squilliden, pp. 140-146. 



3 Metamorphose dei Squillideu, pp. 132, 133, 134, 135, 136, and 138. * Metamorphose der Squilliden, p. 154. 



