Gdtty Marine Lalioratory, St. Andrnoi^. 2-''i5 



system forms a subliy podermic band resting on the basement- 

 tissue, and which Claparede interpreted as a transverse 

 commissure between the ganglia f*, yet to be considered as 

 the representative of tlie cerebral ganglia, and the two eyes 

 in Telepsarus rest on it. The ventral cords, moreover, show 

 no ganglia and are wide apart. He does not allude to the 

 minute structure of the nerve-tissue. 



In 1885 von Drasche f gave a careful account, with figures, 

 of the structure of Owenia ^^filiformis " as it occurred at 

 Trieste, dealing in the first instance M'ith the external 

 characters, and especially the " Lippenorgan^' at the oral 

 aperture, the hypoderm and nervous system, the muscu- 

 lature, alimentary canal, coeloniic cavity, and long mucous 

 glands. So far as he goes, the structure of these organs is 

 correctly described, with accompanying figures. He could 

 not satisfy himself as to the " nephridia " and the mode of 

 exit of the genital products. He observed no nerve-cells in 

 the minute structure of the central nervous system or in the 

 ventral cord, only a fibrillar structure and Leydig's punctate 

 substance. The ventral cord showed no ganglionic enlarge- 

 ments. Below the epithelium of the alimentary canal a 

 strand similar in structure to the central system is briefly 

 mentioned, but nothing definite is recorded concerning 

 the nerve-supply of the internal organs nor concerning the 

 nephridia. 



in looking around for analogous relations of the central 

 ganglia, it is found that in Phoronis Cdldweli X observed that 

 the central nervous system remained in the epidermis, and 

 therefore represented the primitive condition. In the adult 

 the central system is in the form of a post-oral ring, the anus 

 lying outside it. In Phoronis buskii of the ' Challenger ' § 

 the nerve-centre rests on a broad plate of basement-tissue, 

 with the hypoderm externally extending from the nephridia 

 forward to the centre of the whorl of tentacles on each side, 

 and it agrees precisely in minute structure with that in 

 Cephalodiscus and Owenia. 



The central nervous system in Cephalodiscus dodeca- 

 lophus II occupies an area of considerable proportional size at 



« Annel. Sedent. p. 127. 



t ' JBeitrage zur feiueren Auatomie der Polycbaeteii,' Zweites Heft, 

 Wieu, pp. 1-22, 2 plates. 



X Proc. Roy. Soc. vol. xxxiv. p. 372. 



§ Zoology, vol. xxvii. part 75, pp. 18-21, pi. ii. figs. 1 & 2, pi. iii. 

 tigs. 1-y 



II ' Challenger,' Zoologv, vol. xx. part 62, p. 23, pi. vi. fig, 3, and pi. vii. 



16* 



