SECT, ix PHYLUM ANNULATA 207 



wounds made by the jaws. Around the pharynx are numerous 

 unicellular salivary glands^ which open close to the mouth : 

 their secretion has the effect of preventing the coagulation 

 of the blood taken as food. 



The pharynx communicates by a very small aperture with 

 the second and largest division of the enteric canal, the 

 huge crop (cr.\ a thin-walled tube extending from the eighth 

 to the eighteenth segment, and produced into eleven pairs of 

 lateral pouches (cr, i, cr. n). The crop is capable of great 

 dilatation, and its form varies greatly according to whether 

 it is empty or gorged with blood. Posteriorly the crop 

 communicates by a minute aperture with the stomach (st.\ a 

 tubular chamber which is the digestive portion of the canal ; 

 the blood is passed into it from the crop with extreme 

 slowness, and undergoes an immediate change, its colour 

 turning from red to green. The digestion of a whole 

 cropful of blood takes many months. The stomach is 

 continued into a narrow intestine (int.} : this passes into a 

 somewhat dilated rectum (rct.\ which turns slightly upwards 

 and opens by the anus (an.) in the last annulus. 



The excretory system consists of seventeen pairs of 

 nephridia (nph. 1-17), situated in segments 6-22. A 

 typical nephridium has the general form of a loop passing 

 upwards from the ventral body-wall, produced into an 

 offshoot which extends inwards (mesially) to the correspond- 

 ing testis, and connected posteriorly with a small bladder 

 or vesicle. The free end is swollen into a lobed mass 

 which lies in a blood sinus : comparison with other 

 Hirudinea shows that this dilated end of the nephridium 

 represents a nephrostome which has lost its open funnel-like 

 end in correlation with the absence of a distinct ccelome. 



There is a complex vascular system, containing, like that of 

 the earthworm, red blood, the plasma coloured with haemo- 



