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DIGESTION AND ENDODERM OF LIMNOCODIUM. 125 
present a spherical appearance, and the first explanation of their 
appearance here which suggests itself, is that they have been 
developed in endoderm cells. But the fact that they are scat- 
tered very irregularly and occur in all regions of the gastric tube 
sporadically is against this view. Further the absence of any 
cells of the endoderm in which stages of the development of 
such nematocysts can be made out is also against the view that 
they are developed here. Lastly, the facts that they are pre- 
cisely similar in appearance and size to the nematocysts of the 
tentacles, and that actual bits of ectoderm cells containing three 
or four nematocysts side by side may be observed occasionally in 
the gastric tube, are in favour of the view that the nematocysts 
occurring in the gastric endoderm have been swallowed by the 
Medusa with its prey, and have become embedded in the soft 
endoderm fortuitously. 
This explanation has been offered by Mr. Marcus Hartogg 
(see this Journal, 1880) of the similar occurrence of nemato- 
cysts in the endoderm cells of Hydra; and for the present case, 
as well as that of Hydra, it seems to me to be satisfactory, 
though it must be remembered that there is no great improba- 
bility connected with the development of nematocysts by endo- 
derm cells unless the mesenterial filaments of the Anthozoa can 
be shown to have an ectodermal origin. 
Above and below the limited region of homogeneous hexagonal 
cells the endoderm of the middle third of the gastric tube 
exhibits two distinct concomitant modifications (Plate X, 
fig. 1). 
1. Some of the cells are enlarged and highly granular (4), in 
fact have become secretion cells or unicellular glands. 
2. The cells are no longer continuous, but here and there the 
cell-pavement is deficient, actual gaps of greater or less size (/) 
making their appearance between neighbouring cells. 
Endoderm of the oral third of the gastric tube.—The endo- 
derm of the oral region presents a condition which may be con- 
sidered as a development of that last described. In Plate IX, 
fig. 3, a plece is represented. All the cells are here either fully 
developed as secretion cells (4), large clear bodies about the 
rs'soth inch in diameter, or are on their way to this condition 
(4). The nuclei have the characteristic form and size (a). The 
intercellular spaces (/) are very small and few, whilst surround- 
ing the enlarged secretion cells and enclosing the yet young 
secretion cells is a sort of laminated matrix (7). This matrix is 
to be regarded as an intercellular substance of a horny or gelati- 
ginous character. It forms a complete framework to the whole 
series of cells, enveloping each of the more fully-grown secretion 
cells in a distinct capsule, which is broken through on the free 
