Gatty Marine Lahoratory , St. Andrews. 237 



reo^ion of this coat secretes albuminoid substances, fat, and 

 urinary products. As will be shown subsequently, stich is 

 a misapprehension of the structure of the peritoneal surface, 

 probably owing to the condition of the accomplished Belgian 

 author's material. 



In connection with Gilson's opinion, for it is nothing 

 more, that the hypodermic canals in the sixth segment are 

 genital ducts, it is noteworthy that Arnold Watson observed 

 the reproductive elements in Owenia issuing from two pores, 

 to the right and left of the anus, a portion of the jjosterior 

 end of the body projecting from the anterior aperture of the 

 tube. Thus Gilson's theory of the advantages of the ante- 

 rior oi)ening of the hypodermic tubes (his genital ducts) 

 lapses, were it only by the thrusting out of the much more 

 delicate tail anteriorly. 



OgnefF* (1899), working at the Naples Station, took up 

 the subject of Gilson's "cellules musculo-glandulaires" in 

 Owenia. In his preparations he found within the muscular 

 layer of the body-w'all a protoplasmic and cellular layer 

 wiiich lined the coelom. In the muscle-fibres of the longi- 

 tudinal coat themselves were spindle-shaped cells with nuclei, 

 as Schwalbe first described in the muscles of worms and 

 lamellibranchiate moUusks, and also on the surface of the 

 muscles in a protoplasmic layer. Over these, however, is a 

 layer of peritoneal cells, w'hich are cup-shaped, with rounded 

 inner or deeper surfaces and flattened surfaces toward the 

 ccelom, with an oval nucleus, fat, and granules like the white 

 of e^^^ in the protoplasm. A fine protoplasmic network 

 stretches from these amongst the muscle-cells. He thought 

 there wei-e as many as fifteen to twenty peritoneal cells to 

 one muscle-cell. He did not consider that Gilson's " muscle- 

 gland-cells" existed in Oivenia, the misapprehension being 

 due to the less elaborate methods of preparation and section- 

 making. 



In 1900 a very interesting paper on Oivenia fiisiformis 

 was communicated to the Linnean Society by Mr. Arnold 

 Watson t, whose observations on the living animals are 

 noteworthy. His description of tlie lip-organ and its func- 

 tions, the occurrence of a prostomial pore^ the discovery of 

 theemi.-sion of the sexual elements through twocoelomo-ducts 

 (anal pores), the structure and repair of the tubes, and the 

 learing of the ova to the Mitraria-stage are the chief features 

 of this contribution to the life-history of the species. 



* Biol. Centralblatt. Bd. xix. p. 136. 



t Journ. Linn. Soc. vol. xxviii. p. 259, pi. xxii. 



