DR M'INTOSH ON SOME POINTS IN THE STRUCTURE OF TUBIFEX. 257 



histological difference between the two sets of cells ; and both differ very 

 much from the cells on the inner surface of the intestinal wall (Plate IX. 

 fig. 13.) 



I have been somewhat minute in observing this point, because it has 

 generally been stated that the perivisceral corpuscles have their origin from, or 

 are closely connected with, the gland-cells which cover the intestine and dorsal 

 vessel. M. d'Udekem is stated by Mr Lankester, in his recent paper on 

 Chsetogaster,* to have connected the two in his memoir on Tubifex, but such is 

 not my impression. It is true the author describes two hinds of " glandules " 

 covering the intestine and the dorsal vessel, viz., nucleated brownish " glandules," 

 and colourless " glandules " having oily contents, and says they represent the 

 liver of the higher animals, — secreting a liquid for assisting digestion. In speak- 

 ing of the perivisceral fluid, moreover, he omits all notice of the origin or rela- 

 tionship of the corpuscles ; and adds that the number and large size of these 

 " globules lymphatiques " constitute one of the differences between the young 

 Tubifex, on its extrusion from the egg, and the adult. He hints at no connec- 

 tion between the two structures. Mr Lankester, also, in the same paper does 

 not fully express the published opinions of M. Claparede on this point. He 

 says, " There is a very distinct relation between the abundance of the perivisceral 

 granules and cells, and the abundance of the brownish granules which surround 

 in masses the dorsal vessel and its ramifications on the stomach or intestine. 

 Claparede, in his 'B-echerches sur les Oligochetes,' has spoken of the brown-yellow 

 ' hepatic ' tissue of the intestine in Lumbricus being continued to and surround- 

 ing the dorsal vessel, and has hinted (but only obscurely) at some connection 

 between the perivisceral cells and the supposed hepatic tissue. "t Now, in the 

 first place, in the memoir alluded to, M. Claparede did not specially refer to 

 Lumbricus so much as to those genera included under his family of " Oligochetes 

 Limicoles" (Tubifex, Limnodrilus, Clitellio, Lumbriculus, Stylodrilus, Enchytrwus, 

 &c), whose structure formed the text of his work. Chcetogaster, of course, 

 would come under the same head. M. Claparede states that the pigment- 

 cells of the intestine have generally been considered as hepatic, and points out 

 that the said cells have as much connection with the dorsal vessel as with the 

 intestine ; that in Lumbriculus variegatus, for example, the cellular coating, 

 which ceases to cover the intestine at the sixth segment, continues on the 

 dorsal vessel to the fourth, and, moreover, the coating follows certain branches 

 of the dorsal vessel. Further, he adds, that the intimate connection between 

 the supposed hepatic structure and the vascular system is extremely evident in 

 the true Lumbrici, and concludes with the following :— " II est done tres-im- 



* Trans. Linn. Soc. vol. xxvi. p. 637. 



f" Mr Lankester has altered his views here. — Vide his paper in the Quart. Jour, of Micros. Sc. 

 vol. v. N. S. p. 109. 



VOL. XXVI. PART. II. 3 X 



