220 Henry Leste OsBorx, 
is still smaller in cross-section. It is difficult to make out, by the 
methods employed in the general histology, the structure of these 
organs, but I am certain that there are two parts comprising them: 
a central solid homogeneous object, and a number of threads on 
the surface embracing the centre part in its long axis. It looks as 
if an axial thread ran from the common origin of the surface 
threads up into the solid centre part. In surface views a ring of 
minute points is seen which I interpret as the ends of the surface 
fibres just mentioned. Sense organs would seem likely to be pre- 
sent frequently in the cuticle of trematodes but very little has been 
written about them by most authors. Wricur & Macanium have 
described organs of this kind in Sphyranura of the hair cell type 
with the hair projecting beyond the general surface. NICKERSON 
(1895) found organs in Stichocotyle which bear some resemblance to 
those of Cotylaspis consisting of a fine filament runing up to the 
surface in the cuticle from beneath. I have been inclined to suspect 
however that in Cotylaspis the surface fibres are the nervous portion 
of the apparatus, or at least are chiefly important. A common 
feature in all these organs is that the nerve in all reaches the 
surface. I may perhaps anticipate an article in process of pre- 
paration on the structure of Clinosotum so far as to say that there 
also I am able to find cuticular sense organs somewhat of this type. 
Sense organs in the cuticle have been reported by Buocumann (1895), 
certain of which, as his fig. 5a, present considerable resemblance to 
these, and in which he is able, not only to recognize an oval cuti- 
cular portion located in a low papilla of the outer cuticle, but also 
a nerve fiber which as here pierces the cuticle and then runs 
inwards to connect with a nerve cell in the parenchyma. 
1) The marginal organs. 
Certain organs of unknown function have been recognized in 
some of the Aspidobothridae and called from their situation “marginal 
organs” (“Randkürper”). They are found on the margin of the 
ventral sucker at the points where the walls of the divisions meet 
(Figs. 5, 6, 7, 9, 10), and hence in C. insignis there are commonly 
twenty in all. They lie in the parenchyma in a triangular area left 
by the junctions of the muscular masses, and curve upward and 
inward in conformity with the outline of the body. Each organ 
consists of three parts, an oval thick-walled part next the surface 
about 0.03 mm by 0.02 mm wide with an extremely fine central 
