DIGESTION AND ENDODERM OF LIMNOCODIUM. 127 
Plate IX, fig. 3. Claus distinguishes two kinds of gland 
cells, corresponding to what I believe to be young and old 
stages of one kind of gland cell. A difference exists in the fact 
that in Charybdzea ciliated cells are interspersed among the 
gland cells, whilst such do not appear to be present in the same 
region in Limnocodium. 
Endoderm of the proximal third of the gastric tube.—As we 
pass upwards towards the umbrella, along the walls of the gastric 
tube, the endoderm cells gradually open out, leaving intercellular 
spaces, and where the tube expands slightly in the horizontal 
plane the characters exhibited in Plate IX, figs. 1 and 2, are 
assumed. ‘This is the region which has already been described 
above in the living condition, and in which intra-eellular digestion 
takes place. 
A comparison of figs. 1 and 2, Plate IX, with figs. 3 and 6 
of the same plate, shows that we have in this region the same 
elements of form to deal with as in the oral region, but somewhat 
differently characterised. There are large inter-cellular spaces 
(7), which are marked off by a somewhat fibrillated or laminated 
framework (d) ; spherical nuclei, which take the carmine staining, 
are scattered irregularly, and have surrounding them a proto- 
plasmic cell substance, which is very deficient in some parts, 
and is aggregated in other parts; it appears to be continuous 
throughout, and is not marked off into separate cells corre- 
sponding to the individual nuclei. Two nuclei are often closely 
approximated, indicating recent division, but I have not met with 
any in process of division. . 
Corresponding to the secretion cells of the oral-gastric 
endoderm are circular or oblong groups of oval bodies of a 
refringent substance (4), which appear to correspond to the 
groups of large granules seen in the living specimens. As now 
seen (after the action of reagents), these groups appear to be 
formed by oval droplets of a homogeneous transparent substance, 
which stain of a pale-pink colour with picro-carmine, and are 
strongly emarginated by the difference of refractive index 
between their substance and that of the material in which they 
are deposited. Whilst representing, in position and size, the 
secretion cells of the oral-gastric endoderm, these bodies have a 
different structure from those cells, and the substance which 
stains pink is unlike anything present in that region. 
Large vacuole-like spaces also occur (ee), in which a few 
dark granules and irregular particles may be observed, whilst 
the substance filling the vacuole is transparent, and stains pink 
with picre-carmine. It also appears to have been precipitatea 
as a homogeneous or excessively finely granular solid by the 
action of the reagents. 
