ON OCR PRESENT KNOWLEDGE OF THE CRUSTACEA. 237 



Willemos-Salim, investigated the metamorphosis of some Crustacea which 

 ■were repeatedly captured in the tropical and sub-tropical parts of the 

 Pacific' 



Among these he obtained many specimens of Amphion, and of its 

 brephalus (larva) not only of the true zosea 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 Amfldon 

 he had examined three specimens, two of which were undoubtedly males, 

 as the testes and branchiaa were plainly visible, the former opening into 

 the last pair of legs. 



He was thus able to endorse Anton Dorhn's researches, wherein he 

 dissected a full-grown specimen which possessed branchias and an ovarj-. 



There is, he says, now no doubt that Ampliion is not a larva, but that 

 there arc several species, and perhaps genera, of this remarkable form. 

 For during the expedition they had captured two very interesting mature 

 animals which are closely allied to Amphion. One of these has enormously 

 long eye-stalks, being as long as the entire body of the animal. Another 

 has, besides the long eye-stalks, the carpus of its several pereiopoda, 

 very broad and paddle-shaped, while the dactylos is very minute. Both 

 these forms, like Amphion, have a ceotral ocular spot and eight pairs of legs, 

 each supporting an ecphysis. But, as a whole, the animal is less flat and 

 more resembles Sergesfes than Ampliion ; and he states also that he has been 

 able to determine that the form described by A. Dorhn under the name of 

 Elaphocaris is the brephalus of a Sergestes. There is, however, one species, 

 he says, which in the brephalus stage is not an Elaphocaris, but a larger 

 and less spiny form, but similar in all other respects. 



The manner in which ElapTiocaris matures into the perfect Sergestes, he 

 has been enabled to determine from the numerous specimens that he 

 collected in tlie Western Pacific. After the first moulting the brephalus 

 gets six more branched legs and loses many spines. It enters the Amphion 

 stage, then moults, throws off the branched legs, gets branchia, and becomes 

 a spiny Sergestes. It is only after this last moulting that the central 

 ocular spot disappears. 



He also observes that very similar to the development of Sergestes is 

 that of Leucifer. The earliest form that he had obtained had no eyes, 

 then sessile ones appear, and the animal then presents the form which Dana 

 has called JErictMna demissa. After the second moulting the eyes are pro- 

 jected on stalks, and very long hairs are apparent on all the animal's 

 appendages, and the animal appears a long and very delicate zosea. It 

 now enters the Amphion stage, but never gets more than four pairs of 

 pereiopoda, and even loses a pair of these when it moults, and puts on the 

 adult form of Leucifer, in which two pairs of pereiopoda are wanting. 



It appears to me that instead of confirming the opinion of Anton 

 Dorhn that Amphion is an animal in the adult stage, the observation of 

 the accomplished naturalist of the Challenger rather induces one to believe 

 that it is only a stage in the development of some of the Schizopod Crus- 

 tacea. The brephalus of Amphion, Sergestes, or Leucifer he has not been 

 able to determine, inasmuch as he had never been able to obtain them. It 

 is singular that Amphion was never taken excepting during the night. 



M. Gerbe ^ says that the central nervous system of the larvte of crus- 



' Ann. Xat. Hist., 4th series, vol. 17, pp. 1G2-3. 

 2 CovqHcs Bendus, M.-^y 7, 18C(j, pp. 10-21. 



