centropygus joseensis 247 



Annulation and Measurements. 



In dealing with the annulation of these leeches it is necessary 

 to define precisely the method adopted in the enumeration of 

 the annuli. The earlier workers counted as first that annulus 

 which completely surrounded the body, so that the male pore 

 was given as opening between the 26th and 27th annuli. 



To make their enumerations tally with those of recent workers, 

 there must be added the four annuli on the dorsal surface of 

 the anterior sucker and the annulus which is immediately below 



Text-fig. 3. 



Lateral view of the posterior end ofC.joseensis. A., position 

 of anus. P.S., posterior sucker. 



these divisions but is incomplete ventralh', where it forms the 

 lateral boundaries of the mouth cavity. 



Again, in regard to the position of the anus, which both 

 Blanchard and Kennel show as between the annuli which are 

 second and third from the posterior sucker, I find that in only 

 two of my specimens is there any indication of the last annidus 

 which marks the dorsal surface of the posterior sucker (Text- 

 fig. 3). 



I have shown in Text-fig. 4 the relations of the nerve ganglia 

 to the annuli, and defined the somites on a neuromeric basis. 

 This figure is drawn from the dissection of a specimen 80 mm. 

 long, and certain details added from the serial sections of 

 a specimen 60 mm. in length. The six specimens which I 

 examined ranged in length from 40 to 130 mm., and in breadth 

 from 3 to 7 mm. 



NO. 266 S 



