PEGANTHA SMARAGDINA. 91 



is seen in a radial section (PI. 19, fig. 8), of thickly crowded spindle-shaped 

 ectoderm cells, some at least of which bear bristles in life. In one instance 

 an otocyst is replaced by a small tentacle (PL 19, fig. 1), — a structure differ- 

 ing in no way, except for its small size and rudimentary condition, from any 

 normal tentacle, but connected at its base with an otoporp. This replace- 

 ment of an otocyst by a tentacle is evidence of the close relationship between 

 these two classes of structures among the Narcomedusae. The otoporpae 

 (PL 19, fig. 3), though less prominent than in other species of Pegantha, 

 are of the usual structure, consisting of densely crowded ectodermal cells 

 enclosing nematocysts ; they extend about half the length of the marginal 

 lappets (PL 19, fig. 5). 



Gastro-vascular system. — The stomach is flat, its outline circular in the 

 smaller specimen, in which no gonads have appeared (PL 19, fig. 5). The 

 mouth, which is widely open, is surrounded by a simple circular lip (PL 14, 

 fig. 1). The fact that the oral wall of the stomach is thin and but poorly 

 supplied with musculature makes it doubtful whether the mouth is ever 

 closed. The canals, both peronial and circular, are so broad that they easily 

 admit of the entrance of a stout probe. In the smaller specimen the ring 

 canal in several of the lappets shows a triangular centripetal process suggest- 

 ing the future formation of a new pair of peronial canals. 



Gonads. — These are simple in this species, each consisting merely of a 

 rounded swelling without lobes or processes, the only subdivisions being an 

 occasional shallow furrow or notch (PL 19, fig. 2). In one instance, however, 

 it seems that a previously existing gonad has been secondarily divided into 

 two, with the formation of a new tentacle and peronia. In the one speci- 

 men, a male, in which gonads are pi'esent, the sexual products are nearly 

 mature, so that it appears that this conformation represents the adult condi- 

 tion in this species. As in other members of the genus, the gonads are 

 supported by gelatinous prominences, which, though large in the adult 

 specimen, do not appear until the gonads develop (compare PL 19, fig. 

 7 with fig. 9). 



Color. — One of the most striking features of this species is its color, the 

 stomach, canals, and gonads being of a deep, opaque, lemon yellow, as is shown 

 in the sketches from life reproduced in PL 14, figs. 1 and 2. This is a pig- 

 ment color caused by minute and highly refractive orange or yellow pigment 

 granules which crowd the ectoderm cells over the regions of the gastro- 

 vascular system. A study of sections shows that these same granules occur 



