1875.] Development of some Pelagic Decapods. 133 



grown specimen of it, which lie dissected, was in possession of branchiae 

 and of an ovary, therefore no doubt a mature form. He also described 

 one of its young stages, which has the number of appendages 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 larvae; and I am now able to -produce drawings, 

 not only of the true Zoea with a simple telson, but also of all the inter- 

 mediate 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 ex- 

 amined 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 Amphionidae 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 systema- 

 tical position of Amphion itself. 



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

 pelagic Crustacea, has described *, 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 fey me in the Atlantic ; bat 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 Elapho- 

 caris stage in the "Western Pacific, I have collected numerous specimens 

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



* V. Siebold und Kolliker, Zeiteehrift fur wissenschaftliche Zoologie, Band xx. 

 p. 662, tab. 31. fig. 28, 



