Langdon, Sense-organs of Nereis virens. 47 



The bodies of the cells of the spiral-organs may be found 

 scattered among the basal processes of the epidermal support- 

 ing cells at a considerable distance and in any direction from 

 the base of the central tube and in such cases the basement 

 membrane of the epidermis is continuous beneath the organs. 

 Sometimes, however, the cell-bodies lie in a group more or less 

 directly beneath the central tube (Plate II, Fig. 41) and then 

 the basement membrane of the epidermis is lacking under this 

 group. Its place is taken by a thin membrane whose homology 

 I have not been able to decide. It is formed of slender nucle- 

 ated strands which resemble much flattened muscle-fibers, and 

 is always convex on its inner surface. Sometimes all the cell- 

 bodies of several spiral-organs lie in the same group and then 

 the membrane under this group is so much curved as to form a 

 sort of pouch projecting centrally. This is always the case in 

 the bases of the palps, in which these pouches often extend be- 

 neath the epidermis a distance as great as the depth of the 

 latter.^ In the gill lobes, the bodies of the cells belonging to 

 a single organ lie in a few groups beneath the central tube 

 among the bases of the epidermal cells. 



The body of each cell is quite large ; its protoplasm is 

 coarsely granular and its nucleus takes a uniform stain and con- 

 tains a large nucleolus. The different cells of the same organ 

 vary greatly in form. Some are oval or broadly elliptical bi- 

 polar cells, but by far the greater number are irregularly shaped 

 multipolar cells (Plate I, Fig. 22 and Plate II, Fig. 41). All 

 of the processes except two seem to be short slender processes 

 which extend in various directions among the surrounding cells. 

 One of the two longer processes is also slender. In living gill 

 lobes taken from animals that have been injected by the methy- 



1 Retzius ('92a) figures, in the palps of Nereis diversicolor, the outline of 

 large "Driise" which exactly resemble the outline of one of the above mentioned 

 pouches when a spiral organ appears in the same section and thus continues 

 the outline of the pouch to the cuticula. The glands of N. virens are compar- 

 atively small and do not project centrally beyond the general level of the base 

 of the epidermis. I at first looked upon these pouches in the palps of N. virens 

 as glands and it may be that Retzius has fallen into the same error in N. diver- 

 sicolor. 



