2g BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



in N. ririiis. The first geiiitiil pinnules are longer than the orals, and they gradually 

 increase inVcngth. The most distal genital and the first of the distal pinnules are the 

 longest, those 'bevond decreasing in length to the tip of the arm. 1\ is usually the 

 first genital pinnule; in the younger specimens it is about 8 mm. long with 11 segments, 

 in tlio old specimen 12 nmi. long with 17 segments. The distal genital pinnules are 

 12 to 14 mm. long with 17 to 22 segments. The pinnules at the tips of the arms may 

 be only about 10 mm. long with 9 or 10 segments. The genital and distal pinnules are 

 composed of round segments the first one or two of which are as long as broad, the others 

 slightly longer than broad. Their distal edges may be produced into a row of fine 

 spfnes. The ends of the pinnules are often strongly curved. The dorsal sides of the 

 last three or four segments are arched. 



Side- and covering-plates are well developed along the arm and pinnule ambulacra. 

 There are two or three pairs of each to every pinnule segment. The side-plates have 

 a broad base produced distally into a column to the end of which the long and narrow 

 covering-plate is attached. In the older specimen the bases of the side-plates along 

 the lower segments of the pinnules are reduced. 



Sacculi are very few and inconspicuous, widely and irregularly spaced. 



As in N. mrilis, the gonads lie in the angles between the pinnules and the arms. 

 Only two of the specimens are males, both rather small and probably far from phj^sically 

 mature. Though they are easily seen from the side the testes are very much smaller 

 and less conspicuous than those of N. mrilis. They are about 1 or 2 mm. long, triangular, 

 and lie ^\ith one side along the first two segments of the pinnule and another along the 

 arm. Regarding the side which runs along the arm as the base, there is near the ape.x 

 but slightly below it on the inside, a small papilla through which Dr. John assumed 

 there is a pore for the passage of the spermatozoa to the outside. 



The female reproductive organs consist of ovaries and brood pouches as in A^. 

 virilis. In the youngest specimens the brood pouch does not touch the ovary of the 

 next pinnule on the same side of the arm. In the older specimen from station 1948 it 

 does. The ovaries are oval, less than 1 mm. long in the younger specimens, about 

 1.5 mm. in the older. Each lies at the base of the pinnule, resting against it and the 

 arm, and is not usually visible behind the base of the pinnule from the outside. The 

 brood pouch lies in the angle between the arm and the pinnule, separated from the 

 ovary by a thin septum in which there is a large round pore. Larvae escape from the 

 brood pouch through a slithke orifice on the inside. The brood pouches are easily 

 seen from the outside and their walls are so thin that the embryos and the ciliated 

 bands of the most developed may be seen through them. There are many more, 

 though much smaller, embryos than in A'', virilis. In the larger brood pouches of the 

 younger specimens there may be over 30 embryos. One of the lower brood pouches of 

 the older specimen was dissected out and found to contain no less than 92 embryos. 

 The embryos vary in size from 0.25 to 0.48 mm. The smallest are globular, and oidy 

 a little larger than the largest eggs in the ovary. The largest are oval with five broad 

 bands of cilia; they are fuUy formed larvae at much the same stage of development as 

 those of A'', mrilis, described by Mortensen, which are four times as long and have no 

 trace of ciliated bands. Presumably thej- pass on to a free swimming stage before 

 settling dowTi and changing into pentacrinoid larvae. The older embryos are found in 

 the distal part of the brood pouch, the younger in the proximal part near the ovary. 

 One brood pouch may contain every stage between the egg and the fully formed larva. 



