122 BULLETIN OF THE 



are therefore strictly of an Astrophyton type, and discharge their products 

 into the body-cavity, which is continuous and uninterrupted by radi- 

 ating partitions. 



Astrogonijihus might very well be called an Astrocnida whose arms 

 do not fork ; and we should expect a genus so closely allied to have a 

 similar internal structure. And so it is. The arrangement of the 

 organs of digestion and rejjrod notion is entirely comparable, except that 

 the folds of the stomach are less complex and numerous. 



Ophiocreas oedipas brings us a long step nearer the true Ophiurans. 

 An opening, somewhat inclined from the vertical, through the base of an 

 arm and the outer corner of the disk, is sketched in Fig. 7. The integ- 

 ument of the arm, cut through on the side, is lifted and thrown back, 

 while the side of the disk is wholly cut away. Above the arm-bones, at 

 the base of the arm, lie the doublo-lobed spermaries, 8, S, long, cylindri- 

 cal, smooth bodies, a little curved, and tapering at each end. On the 

 opposite side of the arm lies a corresponding pair. The genital open- 

 ing, no, enters a spermatic pouch, or bursa, separated from the body- 

 cavity, as in Ophiurans. An extension of the lining membrane of this 

 bursa encloses the spermatic lobes, 8, 8, which discharge into it by a 

 pore at their inner end. I have already remarked (Bull. Mus. Comp. 

 Zool., VI. 2, p. GG) that the ovaries of this species lay in the same 

 position, at the base of the arm. I made, however, a mistake as to the 

 "large eggs which are about .7 mm. long." They are not eggs, but 

 clusters of eggs, each wi'apped in its membrane and comparable to th(;se of 

 Astrogomphus. The position of the genital organs, though curious, is 

 not so exceptional as might at first appear. Among true Ophiurans, 

 the space between the stomach and the sides and roof of the disk-wall is 

 crammed with these organs when gravid. In Ophiocreas, however, not 

 only is the disk small, but its body-cavity is limited to the perihsemal 

 canal and to a sinus over each arm. Everywhere else the stomach ad- 

 heres to the body-wall ; therefore the genital organs are, as it were, 

 forced into the space between the skin of the arm and the arm-bones. 



The dissection of a female Ophiocreas (an undescribed species from 

 the "Blake" dredgings) demonstrated the homology of the genital or- 

 gans with those of Ophiurans. Tliere were two long lobes, or tubular 

 membranous bags, on either side of tl)e upper surface of the arm. 

 These were in process of discharging their eggs, which takes place by 

 the l»reakiiig up of the egg-clusters and tlie passage of the eggs to the 

 inner end of the bag, where they go, through a pore, into the bursa, 

 which is merely a hjbed indentation of the disk -wall, and is even some- 



