144 Macteay Memorran Vouume. 
layer is of similar character in the two groups, and the presence of cilia in 7. mznor 
and 7. Dendyi makes the resemblance very close. The basement-membrane is 
absent in the Rhabdoce/a, but it would not appear to be present in all the species of 
Temnocephala (Weber). 
A striking similiarity between the Zemnocephalee and the Rhabdocela is in the 
presence in both of the system of unicellular integumentary glands forming rhabdites 
(Stiibchen). The arrangement of their ducts in the former as they run forwards in 
the anterior region of the body into broad strands or “ Stiibchenstrassen ” precisely 
corresponds to what occurs and what I myself have seen in many Rhabdoceeles; and 
nothing of the kind appears to have been observed among the Trematodes. 
The structure of the pharynx is similar to what obtains in some of the 
Rhabdoceeles, such as AZesostomum, but, on the other hand, it appears equally near 
to that of the corresponding organ in Polystomum, Sphyranura and certain other 
Monogenetica. The intestine and its epithelium closely resemble those of a 
Rhabdoceele, with the exception of the constrictions, which never occur in the latter. 
The excretory system is quite peculiar, so far as our knowledge extends. It 
more nearly resembles that of the ectoparasitic Trematodes than that of the 
Rhabdoceeles ; the contractile, pulsating, terminal sacs being absent in the latter 
group, and almost universally present in the former. Of the five types of arrangement 
of the vessels described by von Graff (p. 105) that presented by Prorhynchus stagnals, 
in which there are two lateral openings towards the middle of the body, from each of 
which a main vessel runs transversely for a little distance to become divided into 
anterior and posterior trunks, approaches most nearly that which occurs in 
Temnocephala. 
In its nervous system 7Zemnocephala exhibits one of the highest types of 
development among the Platyhelminthes, with its comparatively large brain, the rich 
development of nerves running forwards, the three pairs of posterior trunks, and the 
highly developed subcutaneous nerve-plexus. But in these respects it does not stand 
quite alone. In 77zstomum mole, as described by Lang,* all these features recur, and 
but for the less development of the anterior nerves and certain differences in the relations 
of the subcutaneous plexus (which in 77zstomum is apparently equally contributed to 
by all three pairs of trunks), there is a very close correspondence between the two. 
Though a subcutaneous nerve-plexus is present in Z777cladide and Polycladide, 
nothing of the kind has been noticed in the Aaddoce/a, and there would appear 
never to be more than one pair of nerve-trunks running backwards from the ganglion 
in that group. The eyes can be exactly matched among the Rhadbdoce/a, and, on the 
* “ Untersuchungen zur vergleichenden Anatomie u. Histologie des Nervensystems der Plathelminthen.” ‘ Mittheil. 
a.d. Zool. Stat. zu Neapel,’ IL. Bd. p. 28. . 
