MORPHOLOGY OF BATH YN EL LA AND ALLIED CRUSTACEA. 501 
mid-gut, although Chappuis applies that name to the follow- 
ing, still wider portion, which extends as far as the fourth 
abdominal somite. In this region the dorsal wall of the gut 
is thick and glandular, while the ventral wall is thin. The 
short rectum is stated also to have a glandular structure. 
The entire absence of hepatic or other diverticula of the 
gut is a feature not paralleled in any other Malacostracan. 
Circulatory System . — The short heart lies in the fourth 
thoracic somite, and does not exceed in diameter the vessels 
that come off from it in the middle line in front and behind. 
No ostia have been seen. While the anterior vessel is no 
doubt an aorta (arteria dorsalis, Chappuis), the posterior 
vessel is described as a “ vena dorsalis ” collecting the blood 
from the sixth abdominal somite and returning it to the heart. 
Such an arrangement would be very unusual, if not unique, 
among Crustacea, and perhaps the so-called dorsal vein 
should be regarded rather as a backward extension of the 
heart itself. In view, however, of the difficulties of investi- 
gation to which Chappuis alludes, it seems possible that a 
mistake has been made as to the direction of the blood-flow in 
this region of the body. 
Excretory System. — Chappuis describes in considerable 
detail the remarkable structure of the maxillary gland. It 
consists of an end-sac (coelomic sac), a looped canal extending 
backwards into the fourth thorncic somite, and a terminal 
vesicle with a slit-like opening ou the outer surface of the 
maxilla. During life the terminal vesicle is thrown into 
rapid pulsation, with opening and shutting cf its external 
aperture, by a muscle attached to its wall. This pulsating 
apparatus is compared by Chappuis with that found in the 
maxillary gland of the remarkable Copepod Phyllogna- 
thopus (Belisarius, Viguierella), where it was first 
described by Maupas, and has recently been investigated by 
Chappuis himself (1914b) in specimens found living in 
company with Ba t h y nella . The similarity, however, appears 
to be no more than superficial, either in structure or, probably, 
in function, for while the pulsating vesicle of Ba thy nella is 
