The South African Hirudinea. 317 



this, of which the innermost two of each side may be double in 

 nature and may be more important than the outermost. 



A yellow marginal band at margin of dorsal surface. 



The ventral surface has the same coloration as dorsal, and is 

 provided with a marginal dark band where it meets the yellow band 

 of the dorsal region. 



All the specimens are poorly preserved internally, and judging 

 from the extended condition they had evidently died some little time 

 before being placed in preservative. This would account for the 

 more or less cylindrical nature of the body, which, in the light of 

 experience, was probably flattened as in the other species. 



The dimensions of a number of specimens are given below : 



12345 6 78 



Greatest length 34232835 32 33 30 24mm. 



breadth 5555 5'5 5'5 4-5 5 ,, 



Length of posterior sucker ... 3 3 3 3 - 5 4 3 - 5 3'5 2 ,, 



Breadth of posterior sucker ... 4334 4 4 3 3,, 



,, between genital pores 454 3 - 5 4-5 4 4 4 ,, 



The species in regard to colour pattern might well be placed in 

 Blanchard's species //. Hildebrandti, but differences of a much 

 more important nature prevent such. Unfortunately we are not in 

 a position to make any note on the papillae, as even if such were 

 present, as they probably were, they cannot be seen in our 

 specimens. 



There is no trace of the groove on the under side of the anterior 

 sucker as is figured by Blanchard in H. Hildebrandti. 



Remarks. It will be readily noted that the various species 

 described, form together a more or less continuous series, which 

 might be regarded as quite sufficient for justifying the inclusion of 

 them all under one specific name, the differences being of no more 

 importance than " local variations." With this to a great extent we 

 are in agreement, but, realising that later anatomical work may 

 result in the removal of all the forms mentioned in this paper into 

 a genus distinct from Hirudo, such a step is extremely inadvisable. 



At the present day the various species of Hirudo, even in its 

 amended and limited condition, are distinguishable almost solely on 

 their colour pattern and the arrangement of papillae. How far these 

 distinctions agree with true specific differences awaits a settlement 

 on anatomical a,nd experimental lines. At the same time a discus- 

 sion in such cases as to whether a species or variety is to be founded 

 serves very little scientific purpose where invertebrates are concerned. 



