VIII 



EGHINODERMATA GENITAL ORGANS 



497 



the axial sinus, etc. with it downwards ; i.e., it is impossible to decide which organ 

 took the lead in shifting. (2) As the gonads which bud from the ring-like strand 

 open into the bursae, which latter, however, open outward orally, it is to some 

 extent explicable why the ring- 

 like strand descends interradi- 

 ally to the bursre. 



The whole problem is still 

 further complicated by the ques- 

 tions : (1) What was the original 

 function of the bursse ? (2) Is 

 the ventral position of the bursse 

 the primitive position ? (3) Is 

 the opening of the gonads into 

 the bursse a recent specialisation 



in the Ophiuroidea ? 



The curved-in portion 

 of the ring -like strand 

 (with the sinus enclosing 



FIG. 39-2. Transverse section through the disc of an 

 Ophiurid (Ophioglypha) at the base of an arm (after 

 Ludwig). 1, Dorsal wall of the disc ; 2, bulging of the 

 it) rUllS along that side Of digestive sac ; 3, bursa ; 4, gonad on the bursal wall ; 5, base 



each bursa which is turned of the arm ; 6 - ventral waU of the disc ; 7) bursal ap 61 ^ 6 : 



, .. : . , . T 



to the interradms. It, 



however, gives off a branch to the wall 



the radius (of the arm), this branch running along this wall from 



its periphery to its proximal part. Both w r alls of the bursa, therefore, 



8, genital plate ; 9, bursal scale. 



which is turned towards 



FIG. 393. Section through an ovary of an Ophiurid (Ophioglypha lacertosa) (after Cudnot). 

 1, Muscle trunk, cut through transversely ; 2, nerve ring ; 3, bursal wall ; 4, aperture of the ovary 

 into the bursa ; 5, wall of the genital sinus ; 6, genital sinus ; 7, the endothelium of the genital 

 sinus, which covers the gonadial wall ; 8, cavity of the gonad ; 9, eggs in a more mature condition 

 than the rest ; 10, ring-like strand in the aboral ring sinus (11). 



the abradial wall, i.e. that turned to the interradius, and the adradial 

 wall, i.e. that turned to the arm, have a genital strand. The abradial 

 genital strand of each bursa is merely a part of the apical ring 

 strand, while the adradial is a lateral branch of that strand. These 

 VOL. II 2 K 



