51 



length. The ventral blood-vessel 

 is also double for the greater part 

 of its length outside the ventral 

 ■sinus; again unlike GalUobdella. 

 The lateral vessels give off 

 branches which run into the 

 branchiae and end with an open 

 mouth. The lateral sinus, which 

 runs parallel to the lateral vessels, 

 ■communicates with the cavity of 

 the respiratory vesicles (text 

 iig. 6). The ovary is situated 

 within the ventral sinus, as in 

 Pontobdella. 



The Nervous System and the 

 Alimentary Canal resemble those 

 of other Ichthyobdellid leeches, 

 and do not present any special 

 features. The various regions of 

 the latter can be best seen from 

 text fig. 7. The saliva^ glands 

 are very well developed, and 

 exhibit in section large secretory 

 cells (text fig. 8). In the leech 

 sectioned only the intestine con- 

 tained a moderate quantity of 

 nucleated red blood corpuscles 

 taken as food from the host. 



The Reproductive System bears 

 a close similarity to that of other 

 Ichthyobdellid leeches. The posi- 

 tion of the genital apertures 

 lias already been mentioned. A 

 general idea of the sexual organs 

 may be gathered from text figs. 

 8 and 9. The male reproductive 

 organs consist of six pairs of 

 metameric testes, situated in the 

 first six segments of the abdomen. 

 The testes are chambered, and 

 contain spermatozoa in all stages 

 of development. From each testis 

 springs a short vas efferens, that 

 from the most posterior one 

 serving as a source of the vas 

 deferens of that side, and in its 

 course received the remaining 



Tk S. 



A. 



Fig. 7. 



Branchellion australis. — 

 Diagrammatic scheme of the 

 alimentary canal in lateral 

 aspect. M., mouth; Ph., 

 pharynx; Ph.S., pharyngeal 

 sheath; S.G., salivary glands; 

 St., stomach; C. coeca ; Int., 

 intestine; A., anus. 



