260 THE VOYAGE OF H.M.S. CHALLENGEE. 



The ovaries consist of deep, lobed, and contorted folds of the lining membrane of the 

 disk wall on its floor, sides, and a portion of its roof These folds are crammed with 

 egg clusters, so as to resemble puddings or sausages (figs. 2 and 3, S, 8) ; and, whatever 

 their form, all end by adhering at their inner margins to the outer ends of the corre- 

 sponding stomach pouches, whose basal lines of adhesion they also continue along the 

 arms, and along the median line of each interbrachial space. As has l_>een said before, 

 the body cavity is thus divided into ten radiating compartments freely communicating at 

 their inner ends by large holes through the partitions. A genital opening enters each of 

 the compartments (fig. 3, n, o). Gorgonocephalus, therefore, has no closed bursa, with 

 its cluster of genital tubes, but the entire body cavity, except the open (periha^mal) ring 

 outside the mouth, is also the genital cavity. It was a similar arrangement that the 

 older anatomists attributed to Ophiurans ; and it is strange that theii- observations were 

 true only of genera that had never been dissected. 



As to internal composition, the ovarial lobes are uniform, and everywhere contain, 

 under a thin, membranous envelope, crowded masses of egg clusters averaging about 

 1 mm. in length, and separated from each other by delicate membranous partitions 

 (fig. 5). The eggs which compose each cluster are round, and about -^ of a millimetre in 

 diameter. The general envelope, as may be seen in the figure, becomes thicker at the 

 free margin, and especially so at points where it grows to the stomach pouches. Its 

 function of supporting the stomach points to its homology with those slender threads 

 that susjjend the Ophiuraii stomach to the body wall. I was not able to detect on the 

 surface of the ovarial lol^es any pores for the egress of eggs, such as exist in the bursa 

 of Ophiurans. It is therefore probable that the membrane ruptures at the breeding 

 season, and the eggs are poured into the radiating compartments of the body cavity. 

 Here the sea water might bring in spermatozoa for impregnation, after which the 

 eggs of any compartment could be discharged through any one of the ten genital 

 openings. 



The chief difference between these organs in Gorgonocephalus and among Ophiurans 

 is the greater specialisation in the latter, where the lining membrane of the disk wall 

 becomes free, and enlarges opposite each genital opening into a closed pouch (bursa), 

 which is extended in the form of finger-like tubes (ovarial tubes). In other words, the 

 lining membrane, instead of l^eing pierced by the genital opening, is continuous and 

 simply becomes free and voluminous. In Gorgonocephalus, on the contrary, the genital 

 opening pierces not only the disk wall but its lining membrane, and enters the body 

 cavity, while nearly the whole of the lining membrane takes on the egg-bearing func- 

 tion, and by the growth of the eggs is gradually stretched and thrown into folded 

 lobes. 



