45 



a large vesicle, does not bear 

 gils, and the third annulus 

 of the twelfth segment is 

 without gills also. Thus the 

 gills corresponding to the 

 first and last pairs of gills 

 present in B. torpedinis are 

 absent in B. austraJis. 



B. Anal region. 3 segments. 



The first two segments are 

 composed of 2 annuli each, 

 and the third of one annulus, 

 making 5 annuli in all. The 

 anus opens dorsally between 

 segments 1 and 2 — i.e., be- 

 tween annuli 2 and 3. 



C. Posterior sucker. 



7 segments. 

 The total number of segments is 

 therefore 34. 

 Respiration. — Respiration is p 

 carried on by means both of the 

 foliaceous branchiae and the 

 rounded vesicles protruding from 

 the abdominal portion of the 

 body. Vesicles are common in 

 other genera, and I have seen 

 them rise and fall by pulsation 

 in Calliobdella lophii. They re- 

 ceive lymph, which after aeration 

 is returned to the lateral sinus, 

 so that respiration is lymphatic. 

 There are 31 pairs of gills, and 

 11 pairs of vesicles arranged as 

 described above. The number of 

 pairs of gills is a specific charac- 

 ter. Blanchard (1894a) came to 

 the conclusion that B. torpe- 

 dinis, (!) which was originally 

 described as having 35 pairs of 

 gills, B. orbiniensis with 33 pairs 

 of gills, and B. rhombi with 30 

 pairs of gills, were all one species, 

 and that the founders of these 

 species had miscounted the gills 

 in everv case, or had stated the 



?t 



Fig. 2. 



Bra nchelUon australis. — The 

 anterior end of the animal in 

 ventral aspect, with the ven- 

 tral portion of the prepuce 

 removed to show the clitellum ; 

 numbering and lettering ex- 

 plained in the text. 31., 

 mouth ; $ , male genital aper- 

 ture ; ^ > female genital 

 aperture; Pr., prepuce; B.V., 

 respiratory vesicle, the first 

 on the left side without a 

 gill; G., the first gill on the 

 left side. 



W The name B. torpedinis was retained as having priority, 

 although 33 pairs of gills was assumed to be the correct number. 



