REPORT ON THE CRUSTACEA MACRURA. 347 



mature form. Ho also described one of its young stages, which has the number of ap- 

 pendages of a Zoea, but in which caudal appendages are already developed. 



" On our voyages in the ' Challenger ' we have caught several specimens of Amphion 

 and of its larva? ; and I am now able to produce drawings, not only of the true Zoea 

 with a simple telson, but also of all the intermediate stages between it and the adult form 

 with two, three, four, five, and six pairs of walking-legs. Of the full-grown Amphion 

 I have examined three specimens, two of which are undoubtedly males, as the testes 

 (and the branchiae) were plainly visible, the former opening into the last pair of legs. 



" There is now no doubt that Amphion is not a larva, nay, even that there are several 

 species and perhaps genera of this remarkable form. 



" We have caught two very interesting mature animals which are certainly closely 

 allied to Amphion. One of these has enormously long eye-stalks, which, having a length 

 of 7 millims., are just as long as the whole animal's body. 



" Another form has got very long eye-stalks too, but is especially remarkable for the 

 antepenultimate joints of its pereiopods, being large paddle-shaped organs, terminated by 

 a very small end-joint. Both have got, like Amphion, a central (Nauplial) eye and 

 eight pairs of branched legs ; but their body is more Sergestes-like and less flat than that 

 of Amphion. They certainly belong both to the same genus, and may be called 

 Amphiones until more than one specimen of each has been obtained. 



" To me these Amphionidse" are especially interesting, as I can compare them with the 

 larvae of Sergestes and Leucifer, the former of which have also got eight pairs of branched 

 legs and the central eye which persists in the Amphionidae. 



" There are good reasons for the statement that the larvae of Leucifer and Sergestes 

 pass through an Amphion stage ; and this, it seems to me, throws a good deal of light 

 on the relations and systematical position of Amphion itself. 



" Dohrn, to whom we owe so many fine discoveries concerning the pelagic Crustacea, 

 has described, 1 under the name of Elaphocaris, a small and very spiny Zoea, caught in 

 the harbour of Messina. He calls it the larva of a Decapod without fixing its position. 

 This small larva was often seen by me in the Atlantic ; but I only lately found out that 

 Elaphocaris is the larva of a species, or rather of some species, of Sergestes. There is, 

 however, one species of this genus in which the Zoea is not an Elaphocaris, but a larger, 

 less spiny form, similar, however, in all other respects to the former. Of the species 

 which develops with an Elaphocaris-stage in the Western Pacific, I have collected 

 numerous specimens of all the stages, from the youngest Zoeas up to the mature animal. 

 The mode of development is very simple. After the first moulting the larva gets six 

 more branched legs and loses many spines. It enters the Amphion stage, then 

 moults, throws the branched legs off, gets branchiae, and becomes a young Sergestes. 

 Only after this last moulting the central eye, hitherto present, disappears. 



1 Zeitschr. f. wiss. Zool, Bd. xx. p. 662, tab. 31, fig. 28. 



