236 Prof. M'liitosli's Notes from tie 



the base of the plumes external to the median space, and is 

 bounded externally by the thick coat of hypoderm and 

 internally by the basement-layer. It extends laterally in 

 the hypoderm along the basal region of the plumes and for 

 some distance along the dorsal side of the buccal shield. In 

 microscopic structure it is minutely cellular and granular, 

 intermingled with fibres, and corresponds generally in 

 position with that in (Jwenia and Myriochele. 



Benham * (1896) described the central nervous system of 

 the " Archiannelida" as in contact\with the epidermis, and 

 pointed ont that in some Polychseta it holds a similar position 

 in the epidermis ; but he does not mention this condition 

 in the Ammocharidse, which he associates with his Spioni- 

 formia, nor in the Cha^topteridae included by Levinsen and 

 liimself under the same group or suborder. 



Gilson (1897-98) devoted much attention to the structure 

 and function of the various parts of Owenia. Besides a 

 careful account of the remarkable secreting glands f? which 

 form such prominent organs, lie has furnished an extended 

 description of the " valves septales " % ^'^^^ o£ " cellules 

 musculo-glandulaires" in the body-wall §. Perhaps the most 

 important contribution is that connected with the " valves 

 septales/' wherein he gives a systematic description of each 

 septum, with its functions, one of the most striking being 

 the second septum (i. e., between the fourth and fifth seg- 

 ments), his sphincter muscle being in the position of the 

 ordinary oblique muscle at its insertion over the nerve-cord. 

 The muscular arrangements of this septum are specially 

 connected with the coelomic fluid and the branchiae. After 

 describing the special apertures in the septa and their 

 mechanism, he shows that apertures at several of these 

 connect the coelom with the exterior ; that in the sixth seg- 

 ment two zigzag cutaneous canals springing from funnels at 

 the septum between the sixth and seventli segments perform 

 the function of genital ducts, since nephridia are absent — a 

 feature of a peculiar character in a Polychset. In his paper 

 on the musculo-glandular cells he states that a peritoneal 

 membrane or coelomic coat proper is absent in Oivenia, tlms 

 resembling such forms as the Nematodes, Acanthocephali, 

 many Annelids and Archiannelids. The body-wall is formed 

 by a combined musculo-glandular coat — that is, it cannot be 

 separated into a muscular and a glandular layer. The inner 



* Caml). i^at. Hist., Worms, Rotifers, and Polyzoa, pp. 243, 255, & 325. 



t ' La Cellule,' t. x. fasc. 2. 



X Ibid. t. xii. fasc. 2. § Ibid. i. xiv. fasc. 2. 



