26 
CHARLES BADHAM. 
lialf that of Callobdella nodulifera, a species parasitic 
on a deep-water fish ; however, the latter has better muscular 
development. It seems that the explanation of these apparent 
exceptions to what appears to be a well-reasoned hypothesis 
can only be gained when the life history of these leeches is 
discovered. The only record of Austrobdella trans- 
lucens being found away from its host is a curious one, a 
specimen being found by Prof. J. P. Hill some years ago in 
the gastric pouch of a jelly fish (Cambessa mosaica). 
The dorsal thick-walled part of the middle gut. — 
In Austrobdella only three pairs of pouches are developed 
in this division (PI. 1, fig. 1, M. g.). The fourth pair of thick- 
walled pouches is present only in a rudimentary state. The 
first pair of pouches lies between the 19th and 20th nerve 
ganglia (Text-fig. 6, M. g.) ; the fourth, which in other 
Ichthyobdellid leeches is placed between the 22nd and 23rd 
nerve ganglia, is represented here by a flexure of the intestine 
(Text -fig. 6, M.g.f.) The cells of the epithelium lining this 
part of the gut have their free surfaces covered with a film of 
densely-placed cilia, so that they present a fringed appearance 
in section, similar to that described by Sukatsclioff as occur- 
ring in Branchellion (1912, Fig. 78). There does not 
appear to be present a section of the gut bearing a ciliated 
epithelium of the usual type, such as occurs in Branch el lion 
and in other Ichtliyobdellids (Johansson, 1896a). Following 
the thick-walled part of the middle-gut there is the posterior 
gut, formed chiefly by the rectum (Text-fig. 6, /?.), which 
opens by the anus on the dorsaf surface of the 27th somite. 
The walls of this portion of the gut are muscular and the 
epithelium is similar to that lining the thick-walled part of 
the middle gut, but is not ciliated. 
The Blood- Vascular System. 
Following the well-known work by Oka in 1894, dealing 
with the blood-vascular system in Clepsine, there appeared 
the investigations of Johansson (1896 b) and Selensky (1906). 
