PHYLUM ANNULATA 



499 



ing 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 

 nephridia (nph. 1-17), situated 

 in segments 7-23. A typical 

 nephridium (Fig. 416) has the 

 general form of a loop passing 

 upwards from the ventral 

 body-wall, produced into an 

 offshoot which extends in- 

 wards (mesially) to the corre- 

 sponding testis, and connected 

 posteriorly with a small bladder 

 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 (/. 1.) : the off- 

 shoot to the testis is known as 

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

 viated in H. australis. 



All these parts are formed of 

 a close-set mass of gland-cells, 

 traversed by a complex system 

 of minute intra-cellular pas- 

 sages or ductules, which finally 

 unite into a comparatively wide 

 inter-cellular tube or duct : this 

 winds through the main and 

 apical lobes, and finally enters 

 the vesicle, which opens pos- 

 teriorly in the second annulus 

 of the segment. The free end 

 of the testis-lobe is swollen 

 into a lobed mass (Fig. 412, nst) 

 which lies in a sinus in connec- 

 tion with the testis. This lobed 

 body is a modified ciliated 



