Chap. VII. CLYTIA BICOPHORA. 305 



wall from which it arises, and the space below it and the base of the calycle is 

 about one third broader than deep. The reproductive calycles {Fig. 6, d e) usually 

 arise from the stolons {g\ but occasionally from the pedicels (E). They are twice 

 as long as the sterile calycles, and one third wider, and present an elliptical 

 outline; the mouth is slightly narrowed, and smooth; the contour is varied by 

 six or seven equidistant transverse ridges, with broad furrows between them; and 

 the pedicel is very short, consisting of only three or four rings. 



The sterile hydrsB have twenty-four tentacles, and, in all "respects, resemble 

 those of C. poterium (PI. XXVIII. Fig. 2, a b a), excepting that in this species the 

 diaphragm (PI. XXIX. Fig. 7, c) is very different. As for the reproductive hydra3 

 {Fig. 6, d e), they are remarkable for their parallel constrictions, giving them a 

 ringed appearance ; but we have never been so fortunate as to see them alive, 

 although this species has been collected by us in September, December, January,' 

 March, and April, during which months it was found to be destitute of these parts. 

 We are obliged, therefore, to limit our remarks to a few observations made upon 

 alcoholic specimens, collected incidentally in August, 1849, in Vineyard Sound, south 

 of Cape Cod, and in August, 1857, at Grand Manan Island, off the most eastern 

 shore of Maine. We cannot say positively whether these calycles produce free 

 medusae or medusae-buds bearing planulae, but are inclined to believe, from appear- 

 ances, that they produce medusa?. At any rate, the breeding season is during the 

 summer, certainly in August, and, probably, also in May, June, and July. 



Proles hydroidea. Embrgologg.-The hydra of this species follows the same mode 

 of development as C. poterium (PI. XXVIII. Figs. 4-10); but the calycle is a 

 simple, thm-walled case, until at least two thirds grown, when the diaphragm begins 

 to develop, in the form of a thin, sharp ridge (PI. XXIX. Fig. 8, c), which event- 

 ually projects straight across the lower part of the calycle, without increasing its 

 thickness beyond that of the wall from which it arises. When the hydra is fully 

 developed, and ready to escape from its embryonic confinement, we find that the 

 calycle, along the elevations of the teeth {Fig. 9, c% and the depressions of the 

 sinuses (c"), suddenly thins, from within outwardly, to an oblique obtuse edge, 

 which, consequently, corresponds to the outer surface of the calycle (see c' and c^). 

 At this border the cap {d d') is attached, and follows all the sinuosities; but it 

 is, unlike the calycle, a very thin, filmy body, and divided into two regions, one 

 of which, just above the edge of the calycle, is puffed outwardly, at regular inter- 

 vals {d-" d% which correspond to the sinuses (c') between the teeth; and the other 

 portion is a smooth arch {d), like a watch-glass, which joins the first along a 

 straight line {d'), trending exactly transversely to the axis of the calycle. 



Clytia intermedia Ag. AdulL — As we have not seen the reproductive calycles 

 of this species, we can characterize it only by the sterile hydra. The stolonic 



VOL. IV. 39 



