272 The Structure of the Annelids. 



names employed by other authors such as fleshy portion of the 

 pharynx (M. Edwards), gizzard (Williams), proventriculum 

 (Oersted), appear very preferable. Are there sufficient reasons 

 for rejecting the names ventricle and glands of the ventricle, 

 employed first by Kathke in reference to the Nereids, and 

 repeated by his successors ? Is it necessary to replace them 

 by oesophagus, and salivary glands ? . . . Salivary glands are 

 usually more or less connected with the buccal cavity, while the 

 glands in question are often twenty or thirty segments behind it. 

 In certain Annelids the posterior region of the intestine follow- 

 ing the biliary region, presents a special appearance. Its walls 

 appear filled with cells containing curious concretions, without 

 doubt destined to be eliminated with the foeces. I call this 

 portion of the intestine the urinary region, though it does not 

 appear to contain uric acid/'' 



The Perivisceral and Circulatory System. — We owe to 

 Quatrefages and Williams, especially to the former, a profound 

 study of the perivisceral cavity and of the lymph which it con- 

 tains. The perivisceral cavity is lined with a delicate mem- 

 brane which is only demonstrable in large species, and which 

 M. Quatrefages attributes the discovery of to himself. Had 

 he searched the works of Delia Ohiaje and Kathke, he would 

 have found the membrane and its name. The structure of 

 this peritoneum (tunica sierosa, tunica 'peritonieale of Delia 

 Chiaje) is subject to great variation. In some species the peri- 

 visceral cavity is supplied with vibratile cilia borne by this 

 membrane. Sharpey was, if I am not mistaken, the first to 

 describe it among the Aphroditians, Williams afterwards 

 observed it on the branchiae of the Glycerians, and I described 

 it throughout their perivisceral cavity. It was also noticed in 

 the Tomopteridians. M. Quatrefages, who only cites en passant 

 the observations of Williams, adds that this ciliary movement 

 was known to him long ago in a number of Annelids, and that 

 it may be seen in all species if any trouble is taken. This 

 opinion is not correct. The immense majority of Annelids do 

 not exhibit a ciliary movement in the perivisceral cavity, 

 except at the entrance of the segmentary organs. I only know 

 a perivisceral ciliation in the following groups : — all the 

 Aphroditians, Grlycerians, Polycirridians, Tomopteridians, and, 

 lastly, in an abnormal Tcrebella — T. vestita. It is striking that 

 all these Annelids, excepting the little Terebella and the 

 A-phrodita aculeata, are totally destitute of vessels, and of these 

 two exceptions, one, the Aphrodita, is an animal of rudimen- 

 tary vascular system belonging to a vesselless family ; the 

 other, the Tcrebella, belongs to a family in general vascular, 

 but of which, one tribe, the Polycirridians, is vesselless. In 

 presence of these facts, I must regard the perivisceral ciliary 



