452 W. A. HASWELL. 
developed a rupture has taken place, so that what were in 
the natural state, closed tubes, assume the character of open 
clefts between the cells. In many cases, however, the closed 
character is retained. Such sections as those represented in 
figs. 26 and 28, which are facsimile copies of photographs, 
show that we have to do with a system of fine vessels which 
run in the intervals between the cells of the epidermis. They 
are superficially placed, and, while their lateral walls are 
formed by the edges of the cells, their outer wall, formed, 
apparently, by an extension of the protoplasm of both the 
contiguous cells, with the “cuticle,” is exceedingly thin, and 
is readily ruptured during the processes of fixing and section- 
ing. The deeper portions of the cells are united underneath 
the vessels by numerous fine protoplasmic filaments. 
In several instances in living specimens I thought I was 
able to trace a connection between this network of capillaries + 
and small vessels of the excretory system, and it appears 
very likely that such a communication exists, and that the 
network is to be looked upon as an extension, perhaps 
respiratory, of the water-vascular system.? That this plexus 
should vary greatly in different individuals as regards the 
degree of distinctness with which it appears, accords well 
with the character of the excretory system in general, in 
which the vessels frequently collapse and vanish completely, 
and, when they are in a contracted state, are quite indistin- 
euishable. 
It is unlikely that the occurrence of this remarkable 
network of channels forming an inter-cellular plexus of 
capillaries in the epidermal layer is a peculiarity of 
Anomalocelus. In fact, there seems to be some evidence, 
if only in certain of the figures of von Graff’s ‘ Monograph,’ 
that the same thing occurs in some other groups of Rhabdo- 
1 1 use this term as a convenient one, though the varying calibre of the 
vessels in question renders it not strictly appropriate. 
2 The only reference which I have discovered to excretory vessels in the 
epidermal layer is Vejdovsky’s statement (28, p. 183) that in Bothrioplana 
blind branches extend into that layer. 
