104< Dr. F. Miiller on the Metamoi-phuses of the Praivns. 



XL On the Metamoi-phoses of the Praums. (First Memoir.) 



By Dr. Fritz Muller of Desterro*. 

 [Plate IV.] 

 Milne-Edwards indicated, as probably the larva of Peneus, a 

 small Crustacean which had previously been referred to the 

 Schizopoda as forming the genus Cryptopus of Latreille. I ob- 

 served several species of small Crustacea approaching still more 

 closely to the Schizopoda, and agreeing with Cryptopus and 

 Peneus in the possession of three pairs of cheliform feet, and 

 have been able to trace them back to Mysis-iovms, destitute of 

 chelae, thence to the form of a Zoea, and one species still further 

 to a Nauplius-f orm, and consequently to that fundamental young 

 form which unites the Rhizocephala and Lernseae with the Cirri- 

 pedes and the numerous group of the Cyclopidae. 



Of the Zoea-form five different species were observed, and 

 some of them pretty plentifully during the whole summer; the 

 unaltered Nauplius-f orm, probably the same in which the animal 

 escapes from the egg, came under notice only once (on the 13th 

 December) f. 



The body of this youngest krva (PI. IV. fig. 1) is destitute of 

 segments, pyriform, 0*4 mill, in length, rounded, and 02 mill, 

 in breadth in front, and diminished behind to ^th of the length 

 of the body, truncated, and slightly emarginated. Near the 

 anterior margin stands a small, black, sharply defined eye. The 

 posterior margin bears on each side a strong straight bristle, of 

 half the length of the body, and near this a short spine. From 

 the lower surface of the body spring six slender feet, furnished 

 with long setae, of which the anterior and intermediate attain 

 four-fifths and the posterior about half the length of the body. 

 The anterior are placed close to the frontal margin, the inter- 

 mediate pair immediately behind these, and the posterior about 

 the middle of the body. The anterior are simple, the intermediate 

 and posterior biraniose ; the posterior branch appears to be the 

 immediate continuation of the stem, and is stronger and, in the 

 hinder feet, also much longer than the anterior branch. No 

 distinct joints are to be detected in the feet, but indications of 

 four or five joints may be seen in the posterior branch of the 

 intermediate feet. A strong bristle, as long as the body, stands 

 with some shorter ones at the apex of the anterior feet ; the inter- 



* Translated by W. S. Dallas, F.L.S., from Wiegmann's ' Archiv,' 1863, 

 p. 8. 



t This proves that, at least at the breeding-season, the parents do not 

 reside in the vicinity of the shore, as otherwise the youngest larvae must 

 have been the most abundant. A species nearly allied to Peneus Caramote, 

 which is frequently eaten here under the name of Camarao occurs sparingly 

 m the market m summer, and scarcelv ever above the middle size. 



