Echiuroirls from Brackish Water. 327 
The cuticle, which is a continuous layer over the surface of the body and the 
proboscis, is seen to consist of the following strata: (i) a deeply staining and refrac- 
tile outer structureless layer {c.i.) appearing as a dark border in sections stained with 
Heidenhain's iron haematoxyhn or Dobell's iron haematin. (ii) Underlying the outer 
layer is a much thicker one {c.ii.), which is clearer, stains faintly and shows a fine 
striation of the type mentioned by Jameson (6) in T. neptuni ; no alveolar layer can 
be distinguished under the second layer of the cuticle of the proboscis, but a distinct 
layer of this type is present in the integument of the body. The epidermis (fig. 7) on 
the dorsal surface of this region consists of large columnar cells {E.c.) measuring 
121' x8/^ with a large nearly circular nucleus 3-5'^ in diameter, lying about the middle 
of the cell, the nucleus has a reticular structure and besides a large nucleolus, a few 
chromatin granules are also seen lying scattered in its substance. The cells are 
set closely side by side, leaving here and there space for the openings of the gland 
cells to be described later. In horizontal longitudinal sections the mosaic appearance 
of these cells is very distinct ; they appear polygonal in outline with the margins of 
the adjoining cells in close apposition. In transverse sections of the proboscis it is 
seen that the columnar cells, below the level of the nuclei, are very much smaller 
than above and end in root-like processes, which are, in places, seen to be connected 
with those of the adjacent cells. I could not in any case trace a distinct connection 
between the cell-roots and the nerve or connective tissue-fibres. The protoplasm 
of the cells is granular, but a fair number of striae can also be seen stretching in a 
vertical direction. The gland-cells {G.c) are unicellular, elongated flask-shaped 
structures with the neck projecting between the epidermal cells and opening to the 
exterior ; the basal part lies as deep as the musculature. The nucleus of these cells 
(which is circular in outline and resembles that of the ordinary ephithelial cells ex- 
cept that it stains deeper) lies in the swollen basal part, where it is surrounded by 
undifferentiated protoplasm. The contents of the gland-cells appear to consist of a 
large number of small granules in a clear matrix. Sensory or trigger-cells of the type 
described by Jameson (6) are present in fair numbers, specially on the lateral mar- 
gins near the distal end. These sensory cells are found in groups, each consisting of 
an elongated body with very granular protoplasm, an oval nucleus lying in the basal 
part, and a small hair projecting out of the cuticle. No direct connection between 
these cells and the nerve-fibres or nerve-cells could be seen. 
There is no sharp basal membrane limiting the basal ends of the epidermal 
cells. There is, however, a distinct layer of cutis {Cu), which consists of a clear ground 
substance with numerous irregularly branching fibres traversing it ; a few elongated 
cells are to be seen connected with the fibres. It appears as if the fibres were direct 
continuations of the cells mentioned above. 
The musculature which underlies the cutis consists of two layers, — (i) an outer 
•longitudinal {L.m) and (ii) an inner circular {Cm.) one. The layer of longitudinal 
muscles is fairly thick and like the circular one consists of fine muscle-fibres running 
side by side. The structure of the fine muscle-fibres is the same as in other Echiuroids. 
Between the muscular layers of the upper and those of the lower surface, the 
