134 CLASS IV. 



Yet, without microscopic investigation, even,, the colour of the 

 organs of propagation is sufficient to point out the difference of the 

 sexes; the testes are distinguished by a milk-white, the ovaria by 

 a yellowish-brown or red colour. In ninety-eight specimens of 

 Echinus PETERS found that forty-three were males and fifty-five 

 females, so that the two sexes are nearly equal in numbers. In 

 Comatula also, MUELLER found the sexes distinct ; the ovaria and 

 testes are here situated on the pinnulce *. In Ophiura, on the other 

 hand, they lie in the disc, round the stomach as ten structures 

 composed of lobes and blind pouches, that run into a pedicle ; in 

 the spaces between every two rays two such structures are placed 

 close together so as to form five pairs 2 . In the Star-fishes they lie 

 in the angles between the rays, and have the form of bunches of 

 beaded strings : in some species they extend into the rays ; their 

 number is double that of the rays. On the dorsal surface, in some 

 species, in each inter-radial space, two spots are found, which are 

 perforated, sieve-like, by numerous closely arranged pores ; these 

 openings allow the ova or the seed to escape. In other species the 

 products of the genital organs, which have been poured into the 

 cavity of the body are probably allowed to pass out by the respira- 

 tory tubules on the back. In the Sea-urchins five ovaries or testes 

 lie on the inner surface of the shell, and fill the spaces between the 

 ambulacral plates. They are of an oblong flattened form, and con- 

 sist of numerous csecal pouches, which open into an excretory duct 

 running through the midst of the organ. The duct then runs freely 

 like a footstalk, by which the testis or the ovary is attached to the 

 upper surface of the shell where it opens. There are thus five such 

 openings, in five pentagonal calcareous plates around the anus. In 

 Holothurice the ovary or testis is a bundle of branched tubes ; these 

 hang by their blind extremities downwards, and open above into 

 a single excretory duct, being fastened to it like a brush. The 

 oviduct or the efferent vessel lies along the anterior portion of the 

 intestinal canal, and terminates near the anterior extremity of the 

 body by a distinct opening on the dorsal surface. Near this canal 



1 They are figured in the Abh. der Berl. ATcad. Ban des Pentacrinus, Taf. v. 

 fig. 17, 1 8. 



2 H. RATHKE Beitrdge zur vergl. Anal. u. Physiol., JReisenbemerkungen aus 

 SJcandinavien, Danzig, 1842, 4to, s. 116, 117. Tab. n. fig. 3 7. 



