296 PROFESSOR FRANK J. COLE 



and living specimens it is contracted and puckered at the edges. At the sides of 

 the mouth, somewhat in front, is a long slender tentacle (the longest on the head), 

 which is directed in a curve downwards and either forwards or backwards. This 

 tentacle can be rotated forwards, and is for ventral touch. Internal and posterior to 

 this on each side is a smaller tentacle with a very expanded base. From the dorsal 

 front border of the mouth in preserved specimens two prominent diminishing ridges 

 pass backwards into the mouth. There is no buccal funnel as in Petromyzon. 



C. The Body Cavity. 



When a median ventral incision is made, and the body walls reflected, we note, first 

 of all, the peritoneum — a thin, glistening membrane lining the body cavity, and through 

 which the muscles of the body wall are plainly visible. Anteriorly in the body cavity 

 are seen the two lobes of the liver, one behind the other, the posterior lobe being rarely 

 partially subdivided into two, whilst between these two lobes on the right a portion of 

 the large gall-bladder projects. The very wide and perfectly straight intestine is 

 noticed passing back to the cloaca from over the posterior lobe of the liver. To the right 

 of the intestine is usually seen the single gonad {i.e. its ovarian portion), which in the 

 individuals predominantly female more or less affects the shape of the intestine accord- 

 ing to the time of year. This part of the gonad is formed in a genital duplication of 

 the dorsal mesentery (mesoarium) on the right side only (cp. Part II., fig. 1), and thus 

 corresponds to the right genital gland. In a female hermaphrodite the ovarian region 

 of the gonad will be found to contain a number of very large elongated oval eggs, whilst 

 in the male hermaphrodite it may not be seen at all without further examination. 



If the posterior section of the intestine be examined carefully (fig. 5), it will be 

 noticed that as it approaches the cloaca it begins to fuse at the mid -ventral line with 

 the body wall — thus forming at the beginning of the fusion a rudimentary mid-ventral 

 mesentery {mes.'). The fusion of the intestine with the body wall, however, at once 

 extends obliquely upwards and backwards [mes."), thus completely obliterating the 

 body cavity below the intestine. The body cavity, hence confined to the roof of the 

 gut, becomes diminished as it is continued backwards, and opens finally into the cloaca 

 by the large, single, median porus genitalis or abdominal pore (p-g.), as elsewhere 

 described. 



The intestine is suspended by a median dorsal mesentery (mes., cp. also Part II., 

 fig. 1). As shown in fig. 5, this mesentery terminates by a curved border a short 

 distance in front of the abdominal pore, and thus the two dorsal halves of the body 

 cavity are in free communication for a short region anterior to the genital pore. This 

 is obviously necessary in order that the large eggs may escape with facility. 



If the anterior extremity of the body cavity be now examined on the right side, 

 and the liver turned over to the left, it will be seen that the pericardial coelom with 

 its contained heart is situated over the anterior extremity of the front lobe of the liver, 



