182 MR J. D. MACDONALD ON THE REPRESENTATIVE 



proportionate bulk, but in general they are much smaller ; and from the delicacy 

 of the test, the body very readily collapses, offering a serious obstruction to the 

 study of their internal anatomy. 



" The test may be described as semi-gelatinous, smooth, and, with the excep- 

 tion of a long cylindrical process, springing from the dorsal region anteriorly, it 

 is everywhere free from angles and projections. The body is full, and rounded 

 in the middle, from whence it rather suddenly tapers towards the anterior and 

 posterior openings, which are simple and very small, closed by numerous narrow 

 and encircling muscular bands. 



" The muscular system is very complex, consisting of circular, diverging, and 

 inter-communicating bands ; four, in particular, ascend at nearly equal intervals 

 upon the dorsal process. The anterior pair, however, soon unite, and form a single 

 slip, which is connected with the others by transverse fibres. 



" As well as I could make out, the lining membrane of the respiratory chamber 

 passes across the base of the dorsal process without entering it. 



" The gill-band is simple and lengthy, communicating at the oral end with a 

 rudimentary epipharyngeal extension of the same structure. The ciliated stripes 

 are very narrow, and do not increase much in width outwardly. The curved 

 ciliated sac at the anterior end of the gill, and the fine ciliated line connecting 

 this on either side with the anterior extremity of the endostyle, were very dis- 

 tinctly visible in the specimens examined. 



" The nervous ganglion occupies a position corresponding with the anterior 

 fixed end of the gill, but on the inferior aspect of the body. The auditory sac, 

 otolithes, and pigment, present nothing unusual. 



" The endostyle is long and narrow, extending from a point above and to the 

 right of the heart to near the branchial opening. The mouth is situate at the 

 posterior extremity of the gill- band, and leads into a distinct oesophagus, which 

 in its turn opens into an elongated stomach, with a large csecal pouch, directed 

 upwards and backwards, intervening. The stomach takes a straight course 

 directly forwards, and gradually passes into the intestine, which is slightly 

 curved downwards anteriorly, where it ends in the vent, immediately below the 

 base of the dorsal process. A small transparent and highly refracting duct, 

 arising by several radicles in the vicinity of the rectum, courses backwards on 

 the right side of the alimentary canal, and having arched to the left over the 

 csecum or proventriculus, it opens into the commencement of the stomach. The 

 office of this system, first made known by Professor Huxley, is not even yet well 

 understood, though I have myself traced it through all the divisions of Tunicata, 

 even in the microscopic compound forms. 



" The heart, compared with the size of the animal, is small, and situate near 

 the posterior extremity of the ' endostyle,'' on the right side of the stomach. 



" On either side of the ventral surface of the body there is a narrow cylin- 



