A434 W. A. HASWELL. 
result of this arrangement of the parenchyma and its vacuoles 
is that in a transverse section the region between the central 
or digestive parenchyma and the superficial layer appears 
divided by numerous vertical lines, while in a horizontal 
section it has, more or less, the appearance of a cross-section 
of a honeycomb. ‘his appears in figs. 9 and 10. 
In the genital region, which occupies the greater part of 
the length of the body, the cells of the testis of each side he 
in the series of spaces to the dorsal side of the horizontal 
plate, while the ovarian cells occupy the corresponding spaces 
on the ventral side, the plate thus acting as a partition 
between the two. The latter must act also as the main 
support for the digestive plasmodium. 
Immediately within the body-wall the parenchyma forms a 
superficial layer, embedded in which are the greater number 
of the Algz and all the rhabdite-forming glands, and in 
which lie also the main nerve-cords and the plexuses to which 
they give rise. 
The whole structure and arrangement of the parenchyma 
in Heterocherus closely resemble those of that tissue in 
Haplodiscus ussowii, as described by Sabussow (24), 
particularly with regard to the horizontal plate and the sets 
of spaces above and below it. 
‘he food consists of a variety of organisms, many of them 
comparatively high in the scale—Rotifers, small Polycheets, 
Entomostraca, small Amphipoda, etc. These are found in the 
large central space, or, if of minute dimensions, may be 
contained in the interior of the smaller vacuoles. 
In the case of Amphicherus cinereus von Graff (15, 
p. 15, Taf. I, fig. 12) describes and figures special cells which 
he looks upon as concerned in the formation of a digestive 
secretion. In the case of Heterocherus the only elements 
at all resembling in appearance and position those represented 
are deep-lying Alge; and nothing of the nature of special 
secretory cells is to be found. 
From the above account of the digestive system of 
Heterocherus it follows that, in this form at least, the 
