596 ROBERT SOHARFF. 



Polygordius group with regard to the muscular system. We also 

 find in this group the same primitive arrangement of a simple 

 longitudinal layer of muscles, and in this simple muscular 

 structure we see no doubt represented the original condition 

 among the Annelids. 



The Alimentary Canal. — Three parts may easily be dis- 

 tinguished in the alimentary canal ofCtenodrilusj)arvulus. 

 The ventral mouth, which has the form of a longitudinal slit, 

 opens into the ciliated oesophagus. This, in its turn, is followed 

 at the beginning of the third segment by the red stomach, and 

 the intestine constitutes the remainder of the alimentary canal. 

 The latter, like the oesophagus, is ciliated, and generally com- 

 mences at the end of the sixth or the commencement of the 

 seventh segment. In Ct. pardalis the cells of the whole of the 

 alimentary canal are ciliated,^ while in Ct. monostylos we find 

 a similar condition as in Ct. parvulus, viz. ciliated cells in the 

 oesophagus and intestine only. The cells of the ventral side of 

 the alimentary canal are considerably higher than those of the 

 lateral or dorsal sides, so as to cause that part to appear from 

 two to three times as thick. The reddish cells of the stomach 

 gradually merge into the ciliated cells of the intestine, that is 

 to say, they become lighter and lighter in colour, and assume 

 the ciliated condition on approaching that part of the alimen- 

 tary canal. At the commencement of the stomach we do not 

 see anything of that kind, but an abrupt change from the ciliated 

 to the non-ciliated condition. 



The oesophagus (fig. 1, oe) is much narrower than the stomach, 

 and attains its smallest diameter close to the mouth, just above 

 the hinder end of the lower lip (" Unterlippe " of Kennel, 

 " Riissel ■" of Zeppelin) . 



This lower lip is situated beneath the mouth, and consists of 

 a broad muscular plate, the anterior part of which being split. 

 I mentioned before that a strong muscle, acting as protractor 

 to this organ, is inserted into the lower portion of the oeso- 

 phagus. 



^ Kennel, loc. cit., p. 383. 



