800 NATURAL HISTOEY OF AQUATIC ANIMALS. 



progress or not. A continuous series of observations would enable him, at all times, to follow 

 the success of his experiments, or determine, perhaps, the causes of his failures. 



The exact number of changes or moltings which take place between the last egg stage and 

 the first stage having the general shape and characters of the adult, is not known. Professor 

 Smith observed three such stages, but supposes others to be wanting. His account of these 

 .stages is as follows : 



"The following observations on the young larva;, after they have left the eggs, have all been 

 made upon specimens obtained in Vineyard Sound, or the adjacent waters, during July. These 

 specimens were mostly taken at the surface in the daytime, either with the towing or hand net. 

 They represent three quite different stages in the true larval condition, besides a later stage 

 approaching closely the adult. The exact age of the larvae of the first stage was not ascertained, 

 but was probably only a few days, and they had, most likely, molted not more than once. 

 Between the third stage, here described, and the last there is probably an intermediate form 

 wanting. 



"First stage. In this stage the young are free-swimming Schizopods 1 about a third of an 

 inch (7.8 mm to 8.0 mm ) in length, without abdominal appendages, and with six pairs of pediform 

 cephalo-thoracic appendages, each with the exopodus developed into a powerful swimming organ. 

 The eyes are bright blue; the anterior portion and the lower margin of the carapax and the 

 bases of the legs are speckled with orange; the lower margin, the whole of the penultimate, and 

 the basal portion of the ultimate segment of the abdomen are brilliant reddish-orange. The 

 antenna} have large, well-developed scales, furnished along the inner margin with long, plumose 

 hairs. . . . The anterior cephalo-thoracic legs, which in the adult develop into the big claws, 

 are exactly alike and no longer than the exterior maxilliptds. The pediform (outer) branch 

 is, however, somewhat stouter than in the other legs, and subcheliform (bearing an imperfect 

 claw); the legs of the second and third pairs are similar to the first, but not as stout. The legs of 

 the fourth and fifth pairs are still more slender, and styliform at the extremity, as in the adult." 

 Very rudimentary branchiae or gills are observed on all of the legs and the external maxillipeds. 

 "The abdomen is slender, the second to the fifth segments each armed with a large dorsal spine, 

 curved backward, and with the lateral angles produced into long spines, and the sixth segment 

 with two dorsal spiues. The posterior margin of the last segment is armed with a long and stout 

 central spine, and each side with fourteen or fifteen plumose spiues or setse, which are articulated 

 to the margin. 



"In this stage the young were first taken July 1, when they were seen swimming rapidly 

 about at the surface of the water among great numbers of Zoea3, Megalops, and Copepods. Their 

 motions and habits recall at once the species of Mysis and Thysanopoda, but their motions are not 

 quite us rapid, and are more irregular. Their bright colors render them conspicuous objects, and 

 they must be readily seen and captured by fishes. They were frequently taken at the surface in 

 different parts of Vineyard Sound from July 1 to 7, and several were taken off" Newport, Rhode 

 Island, as late as July 15, and they would very likely be found also in June, judging from the 

 stage of development to which the embryos had advanced early in May in Long Island Sound. 

 Besides the specimens taken in the open water of the Sound, a great number were obtained July 

 from the well of a lobster-smack, where they were swimming in great abundance near the 

 surface of the water, having undoubtedly been recently hatched from the eggs carried by the 



1 Tlii' Schi/.opods arc a uronji of Shrimps, lower in orp;aiii/i.tion Ilian our common Shrimp (Cniiii/nii rultjHrix), and very 

 abundant along the New Kn^laiid coast. Th.-y generally swim in large schools, either at the surface or at intermediate 



ili-pllis liri , ui-lacc and llie bollom, oltcn at some distance from land. ' 



