80 EDGAR J. ALLEN. 



ming's solution. These glands will be distinguished as the 

 reticulate and the clear glands. 



The reticulate glands lie, for the most part, just outside the 

 epithelium of the artery of the axis, and are so numerous that 

 two or three of them are found cut across in almost every trans- 

 verse section throughout the length of the axis. The glands 

 are spherical in shape, a point which can be easily demon- 

 strated by following a series of sections, and which is also 

 proved by the fact that in whatever direction the axis of the 

 gill be cut the section through each gland is circular. The 

 conical cells of which the glands are composed have large, 

 spherical nuclei, which lie near their bases, and a dark spot is 

 seen near the middle of the well-formed network in the proto- 

 plasm (fig. 9). 



Close to the centre of each gland a spherical nucleus (figs. 

 9 and 10, c. n.) is invariably found, which is easily distinguish- 

 able from the nuclei of the cells, both by its position and by 

 the fact that it stains less deeply than the latter. On the 

 opposite side of the centre to this nucleus a duct arises (figs. 

 9 and 10, dct.), which can frequently be followed as far as the 

 edge of the gland, as in fig. 9 {dct.), whilst in favorable cases 

 it can be traced into the ectoderm (fig. 11, a, b, c, d, dct.), or 

 even to the exterior (fig. 12, b, dct.). The most probable ex- 

 planation of these relations is that the nucleus [c. n.) belongs 

 to a central cell which has given rise to the duct of the gland, 

 such modification of a cell into a duct ("drain-pipe cell") 

 being common amongst Crustaceans.^ 



At the centre of each gland a star-shaped figure is always 

 well developed. When viewed under a high power {-^ oil 

 immersion) this figure (fig. 10) is seen to be formed by the 

 projection of very fine tubes {tu.) from the ends of the conical 

 cells into the central cell. The cut ends of the tubes belong- 

 ing to the cells below can be seen as dark spots in the centre 

 of the star-shaped figure even under the lower power (figs. 9, 

 11). With the high power these dark spots are seen clearly 



1 Cf. Grobben, "Die Anteunendriise der Crustaceeii," ' Arb. a. d. Zool. 

 Inst. Wien,' Bd. iii, 1881. 



