No. I.] SPHYRANURA OSLERT. 



25 



fresh and in fixed conditions. A large number are to be ob- 

 served in the caudal region in the middle line anterior to the 

 acetabula ; but they are not confined to this point, being more 

 or less scattered throughout the body. They are usually of a 

 polyhedral shape, sometimes with short processes at the angles, 

 and they measure generally 37-50 ^, while the nucleus, when 

 it is observed in a spherical condition, measures 18-20 ^. 

 The cytoplasma forms coarse trabeculae, usually radiating from 

 the centre of the cell to the periphery, Fig. 12, c, and contain- 

 ing a system of communicating spaces empty in the fixed, but 

 often unobservable in the fresh, condition. The trabeculae 

 themselves contain a quantity of granules. The cell has a 

 definite membrane, and applied to it are the united ends of 

 the trabeculae. Nine-tenths of the nuclei have a curved or cres- 

 cent shape, fitting into the concave side of which is a large, 

 clear space of varying outline, sometimes circular ; but the 

 nucleus loses its crescentic form and becomes spherical in speci- 

 mens which have been subjected to pressure for some time. 

 The cell usually does not stain, while the nucleus takes a feeble 

 red color, sometimes, however, a gray tint. A nuclear recticu- 

 lum can be observed, having large meshes, and containing one 

 to several chromatin nucleoli of variable size. Each cell has a 

 process at one pole, with an axial wavy channel connected 

 with one of the neighboring excretory capillaries. Fig. 12, 

 a, the wall of which passes insensibly into the membrane of 

 the cell. 



The structure of these cells was determined only after the 

 various methods of preparation were employed ; the only 

 method which we found satisfactory being that detailed above, 

 p. . Treated with solutions of corrosive sublimate and acetic 

 acid, of chromic acid, or of picric acid, they appear like branched 

 connective tissue-cells, or like unipolar ganglion-cells, and in the 

 caudal region, where they are most abundant, they, with the 

 excretory trunks, give the appearance of retiform tissue with 

 great lacunar spaces. We first believed these cells to be analo- 

 gous to those in Planaria torva, described by Lang' as perfo- 

 rated by the large excretory channels. Some support was given 

 to this opinion when cells were observed apparently similar to 



' Der Bau von Gunda segmentata, etc. Mitth. aus der Z06I. Stat., Zu Neapel., 

 Bd. TIL, p. 187. 



