igoy.] Records of the hidian Afuseiim. 235 



varying in length all are of the same type. The ventral bundles 

 contain usually from four to six setae ; the dorsal bundles contain 

 from two to six and are, on the average, somewhat longer than 

 the ventral. The general length of the setse may be said to be 

 about equal to the diameter of the animal. Both groups of setse 

 begin in the second segment. 



Body-cavity. — There are no lymph-corpuscles in the body- 

 cavity. There is one very definite septum, at the sides of the 

 pharynx, representing the division between first and second seg- 

 ments. Besides this there are a large number of connecting strands 

 between the alimentary tract and the body-wall : they are fine 

 and thin in the region of the pharynx, thicker posteriorly between 

 the intestine and bod}"- wall, where they have a granular proto- 

 plasmic appearance. At the site of a future division they are 

 thicker and more numerous, the condition almost amounting to 

 a fusion between intestine and bod3"-wall. Numerous strands are 

 inserted into the dorsal blood-vessel. 



Alimentary tract. — The mouth is bordered ventrally by a 

 prominent lip, mobile and ciliated. There is no buccal cavity 

 separate from the pharynx ; the oesophagus occupies the second 

 and third segments and is of approximately uniform diameter 

 throughout ; bunches of oval or spherical granular cells ma}'' be 

 seen attached to it in a grape-like fashion, especially posteriorly 

 {v. pi. viii, fig. 3). The stomach occupies segments 4-7 ; it is not 

 very sharply delimited from the intestine ; it may contain in its 

 wall a number of spherical colourless globules, or perhaps vacuoles, 

 about the same size as the green bodies in the skin. The intestine, 

 which follows, may also contain a number of particles in its walls ; 

 but these are more refractile, less regular in shape, somewhat 

 smaller, of a faint bluish tinge, and are apparently of the same 

 nature as the similar bodies described in the skin ; they also occur 

 in the wall of the dorsal blood-vessel. Antiperistalsis is frequently 

 observed throughout the length of the alimentary canal as far for- 

 wards as, and sometimes including, the stomach ; and a reversed 

 ciliary action (postero-anterior) is constantl}' going on in the intes- 

 tine. Diatoms and mineral particles are found in the stomach 

 and intestine. 



Vascular system. — The blood is colourless and contains no 

 corpuscles. The dorsal vessel is contractile ; it bifurcates in 

 the prostomium in front of the mouth, and the branches unite to 

 form the ventral vessel beneath the pharynx. There are no trans- 

 verse commissures. 



Nephridia. — The nephridia are coiled tubes, with small ciliated 

 funnels lying unattached in the bodj^-cavity. The first occurs be- 

 hind the first setal bundle ; seven may sometimes be distinctly 

 counted, while at other times there are apparently only six. None 

 appeared to be modified in any way. 



Nervous system. — The cerebral ganglion appears under two 

 shapes; sometimes as a simple, transversely placed oval mass, 

 sometimes having in addition two lateral, posteriorly directed. 



