ZOOLOGY 



SECT. 



II 



.31 



tubular chamber with a dilated an- 

 terior end, and having its wall pro- 

 duced internally into a spiral fold : 

 this is the digestive portion of the 

 canal; the blood is passed into it 

 from the crop with extreme slow- 

 ness, 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 (ret.) 

 which turns slightly upwards and 

 opens by the anus (an.) in the last 

 annulus. 



The excretory system consists 

 of seventeen pairs of ectonephridia 

 (nph. 1-17), situated in segments 

 6-22. A typical nephridium (Fig. 

 375) has the general form of a loop 

 passing upwards from the ventral 

 body- wall, produced into an offshoot 

 which extends inwards (mesially) to 

 the corresponding testis, and con- 

 nected posteriorly with a small blad- 

 der or vesicle (vs.). The principal loop 

 is divisible into two chief parts, the 

 main lobe (m. I.) and the apical lobe 

 (a. I), connected with one another 

 by a short recurrent lobe (r. I.) : the 

 offshoot to the testis is known as 

 the testis-lobe (t. I.) ; it is absent in 

 H. quinquestriata 



All these parts are formed of a 

 close-set mass of gland-cells, tra- 

 versed by a complex system of 

 minute intra-cellular passages or 

 ductules, which finally unite into 

 comparatively wide inter-celluk 

 tube or duct : this winds througl 

 the main and apical lobes, and final b 

 enters the vesicle, which opens pos 

 teriorly in the last annulus of th( 

 segment. The free end of the testis- 

 lobe is swollen into a lobed im 

 which lies in a blood sinus (Fij 



