ANTEDON. 401 



the branches widen out enormously to form ovate cavities, 

 the gonads (PL VI., fig. 61, tes. ; fig. 62, ov.), which equal 

 in length five or six of the pinnular joints, and, at the 

 period of sexual maturity, are filled with spermatozoa, or 

 ova, derived from the germinal epithelium. 



The testes are invested by a delicate layer of con- 

 nective tissue in which there are oblique muscular fibres ; 

 on the inner side this layer is thrown into many project- 

 ing folds, which greatly augment the surface upon which 

 the spermatoblasts are developed. The mature sperma- 

 tozoon has a conical head and a middle piece to which the 

 tail is attached. Many of the germinal cells which line 

 the ovaries remain small and form a follicular investment 

 around the developing ova (fig. 62, fol. c). 



The course of the genital sinuses and the included 

 genital strands in the disc is very difficult to trace. The 

 sinuses almost certainly open into the circum-cesophageal 

 plexus, but, in the adult animal at least, the genital 

 rachids are not traceable into continuity with the oral 

 end of the axial organ, from which they are said to arise 

 in the larva. A sexually mature Antedon may be easily 

 recognised by its swollen pinnules, to which the extruded 

 ova, which are fertilised externally, adhere in little 

 groups for four or five days, and until the embryo within 

 has developed the rudiments of its skeleton. The gonads 

 of the more proximal pinnules appear to be the first to 

 ripen. The eggs probably escape from the ovaries by 

 rupture of their walls at one or more points of least 

 resistance, while the spermatozoa are discharged through 

 a small funnel-like projection upon one or both sides of 

 the gonad (fig. 61). Sexual maturity occurs in the 

 months of May and June around the Isle of Man, but 

 the time differs a little according to geographical position. 

 According to Cuenot, it occurs in March and April in the 



