Benham. — Neio Species of Leech (Hirudo antipodum). 189 



in the formol specimens when I examined them on arrival, 

 but at the present time I find it more difficult to distinguish 

 them ; and they were much less evident in the alcohol speci- 

 mens. In the formol the sensillae appeared of a different 

 tint from the surroundings — of a more orange colour ; and the 

 sense-organ at the tip of the papilla was whitish. 



With regard to the head, I carefully looked for any pre- 

 ocular annuli, such as Castle* refers to, but there are none 

 in this species. Indeed, the first distinct annulus crossing 

 the body transversely is that which carries the 3rd pair of 

 eyes. The anterior semicircular margin of the head is 

 marked by a series of furrows at right angles to the margin, 

 and traceable on to the ventral surface into the oral sucker. 

 Thus, at the extreme anterior extremity the grooves are 

 sagittal, and as we trace them backwards they gradually 

 assume a more transverse direction till the 3rd eye is 

 reached. These furrows delimit small quadrate areas, and 

 of these there is a couple between the right and left eye of 

 the first pair — i.e., one on either side of the median line. The 

 1st eye lies in the second of such areas ; then between the 1st 

 and 2nd eye is an area ; the 2nd eye occupies one ; then 

 another between 2nd and 3rd eye. These small areas appear 

 to bear the same relation to these eyes as does the annulus 

 between the 3rd and 4th eyes. It may be that each such 

 "area" represents an annulus of some primitive leech, but 

 I find no mention of them in Whitman's paper, though in the 

 beautiful drawing by a Japanese artist of HceDiadijJsa japonica 

 (pi. xvii., fig. 6) similar "areas" exist, having the same 

 general arrangement. In this case, however, they resemble 

 the quadrate, flattened papillae which cover the surface of 

 the body generally. My material of hirudineans, and the 

 literature at my disposal, does not permit me to pursue the 

 subject further; but as we have reason to believe that the 

 " head " is composed of abbreviated somites, and this ab- 

 breviation is more or less marked in different genera, it seems 

 a possible view that these "areas" have some connection with 

 the missing annuli of the ocular region. 



The first complete annulus is the 5th. This " buccal " 

 annulus forms the edge of the hinder margin of the oral 

 sucker, or mouth ; and it is distinct from the 6th, though it is 

 very narrow in the ventral region. 



The genital pores have the usual position — viz., between 

 the 30th and 31st annuli ; and between the 35th and 36th 

 there is a fairly long protrusible cirrus. I have been unable to 

 detect the nephridiopores. 



* Castle. Proc. Amer. Acad. Arts and Sci., Philadelphia, xxxv., 1900, 

 p. 285. 



