No. 15.— On the Development of PALAMONETES VULGARIS. 
By WALTER Faxon, 
"Tig observations recorded in this paper were made during the sum- 
mers of 1876 and 1877 in the laboratories of Mr. Alexander Agassiz, at 
Nowport, R. L, and of the United States Commission of Fish and 
Fisheries, at Wood's Hole, Mass. I am under great obligations to Mr. 
Agassiz, and Professor S. F. Baird, United States Commissioner of Fish 
and Fisheries, for placing at my disposal every means for the collection 
and study of specimens. 
Tho difficulty of rearing the larve of Crustacea in confinement, and 
the uncertainty of finding all the stages in the development of a species 
by collecting with the hand-net or tow-net, perhaps account for the 
fact that we have so few life-historics of Decapod Crustacea which are 
in any way complete. 
The common prawn of our coast, Palwemonetes vulgaris Stimpson, is 
one of tho most typical of the long-tailed Decapods, and affords au 
excellent opportunity for obtaining the life-history of a Macrouran, 
which undergoes a metamorphosis after quitting the egg. The present 
paper is a contribution to that history. 
The opacity of the eggs and larvas making it impossible to follow the 
development of the internal organs in detail, I havo confined myself 
chiefly to the growth of the hard parts. 
'This species was first described by Say, in 1818, under the name of 
Palemon vulgaris ; * again described, and figured for the first time, by 
De Kay, in 1844.+ In 1869, the genus Palemonetes was established 
by Heller for the reception of Palæmon varians Leach, from tho North 
Sea and fresh waters of the Mediterranean basin.{ It differs from 
Palemon in lacking mandibular palpi. In the armature of the carapace 
it agrees with Palcemon, subgen. Leander, i. e. an antennal and a 
branchiostegal spine are present, but no hepatic spine. 
* An Account of the Crustacea of the United States. Jour. Acad. Nat. Sci. Phila., 
Vol. I. pp. 248, 249. 1818. 
t Zoology of New York, Part VI. Crustacea, pp. 29, 30, Pl. IX. Fig. 30. 1844. 
t Zur nüheren Kenntniss der in den süssen Gewässern des südlichen Europa 
vorkommenden Meerescrustaeeen. Zeitschr. wissensch. Zool, Vol XIX. p. 160. 
1869. 
