214 
Calliohdella lopldl 
inter alia, Blanchard found non-respiratoiy vesicles on the preclitellum, 
and 12 respiratory vesicles instead of 11. I have no doubt that Johann- 
son and I have been describing the same animal, which is the Calliobdella 
lophii of Van Beneden and Hesse. The confusion originally arose out 
of Van Beneden and Hesse’s faulty counting of the respiratory vesicles, 
and giving in their figures a different number from that mentioned in 
their text. 
I allude to this more particularly since W. A. Harding (in Parasi- 
tology, Vol. III. No. 2, 1910) in his paper on the Hirudinea, describes 
an animal which he calls Trachelohdella, and in his descriptions follows 
VJ 
w 
® - 
0 
va; 
0 
, X 
w 
,-x 
A 
B 
C 
D 
Fig. 5 (after Johaimson). A comparative scheme of the condition of the caeca in various 
Ichthyobdellid leeches, showing the reduction from two to one. 
A. Abranchus hrunneus. B. Abranchus microstomus. C. Platyhdella anarrhichae. 
D. Piscicola geometra. E. Calliobdella nodulifera. 
X. The aperture from the stomach. 
Blanchard, upholding that author rather to the disparagement of 
Johannson. Harding mentions catches, one by T. Scott in Scotland 
in 1901, which probably were Trachelohdella, though the number of 
respiratory vesicles is uncertain, and the reproductive system does not 
appear to have been investigated. Harding follows Blanchard in good 
faith, but I cannot uphold him in saying that the genera Calliobdella 
and Trachelohdella are one. 
Another alternative remains, namely that the number of respiratory 
vesicles is variable ; but then one would have to suppose that the 
presence or absence of non-respiratory vesicles on the preclitellum is 
variable also, I think it is more than a coincidence that makes the 
