378 ANATOMICAL CHARACTERS OF PEROPHORA HUTCHISONI. 
still further concealed by the gritty coating. The former is situated on the upper surface 
near the free extremity, holding a subterminal position, so that in the mutual relation- 
ship of these openings, Perophora, and indeed also other pedunculate forms, may be 
said to exhibit an approach to Boltenia. 
The surface of the mantle is beautifully marked with yellow branched and reticulated 
lines, similar, no doubt, to those which have been noticed in Clavelina, indicating the 
distribution of vessels. | | 
The endostyle occupies a portion of the dorsal surface extending from near the 
branchial opening to the inner extremity of the sac, where it presents a slight curvature 
towards the oral orifice. 
The transverse bars of the respiratory network are about five in number, and join the 
endostyle in a direction nearly parallel with a line drawn through the branchial and 
eloacal openings, while the much smaller and more numerous longitudinal nervures lie 
parallel with the endostyle. The beautiful network so formed is invested with a stout 
epithelium, and its meshes are fringed with vibratile cilia. 
The mouth is situated at the anterior and inferior part of the respiratory cavity, and 
opens into a short cylindrical æsophagus which passes downwards and backwards to join 
a comparatively small and subglobular stomach. The intestine arises from the dorsal 
surface of the latter organ, and after having performed a graceful flexure by turning 
forwards and outwards, terminates in a very ample atrium or open space between the 
exterior of the branchial network and the muscular coat. The lining of this space is very 
obviously continuous through the branchial slits with that of the respiratory chamber. 
The generative organs, as in most compound Tunicata, are included within the intes- 
tinal loop, and, on account of the close proximity of the cloaca, the ducts are necessarily 
very short. dr 
Two distinct canals, alternately interchanging the office of artery and vein, are eircum- 
stantially described. as occupying the pedicels of the British species of Perophora, but I | 
cannot say that I have found such to be the case in the Australian one. There is, how- 
ever, much difficulty in determining the question, on account of the obstacles which the 
superficial gritty particles and the pigmentary matter of the mantle and tubules oppose 
to the observation of the vital phenomena of the animals. I think I may safely affirm - 
that no such arrangement is traceable in Didemnium, Botryllus, and numerous other 
Tunicata, both simple and compound, that might be adduced ; and if it be actually present 
in the British Perophora, I cannot help regarding the fact as something quite exceptional 
in the group. + 
May 1858. 
