THE LEECHES OF MINNESOTA 101 



Somites I, II and III are each uniannulate; IV is also practically 

 uniannulate but shows some signs of division above in the Pepin ex- 

 ample and below is largely united with V. The latter, together with 

 VI and in the type, VII also, is biannulate, an interesting feature be- 

 ing the rather larger size of second annulus. Somite VIII is quadrian- 

 nulate, being composed of aila2lb$/b6, the latter two being very nar- 

 row. 



Somites IX to XXV inclusive may be regarded as complete, but 

 some individual variations are exhibited and especially the first two 

 and the last are transitional. In the original specimen the complete 

 somites are sexannulate, the full number of secondary annuli being 

 developed, but of very unequal size. Two annuli, (bj and bj) 

 are enlarged, the latter most so. and bear the dorsal cutaneous 

 papilla;, and the former the metameric sensillge as well ; bi, b2 and b6 

 are about equal and b-f is the smallest of all. The small annuli bi, bj 

 and b6 appear to be entirely unadorned, while b2 like the large papil- 

 lated annuli exhibits a circle of sense organs. 



The conditions in the new specimen are essentially similar, but 

 the somites are somewhat further elaborated. Somite VII is triannu- 

 late rather than biannulate, VIII has the small annuli bi and b^ 

 rather distinctly separated and there is a very strong tendency in the 

 anterior part of the post-clitellial region toward the splitting off of 

 small additional annuli from the anterior margins of the enlarged an- 

 nuli &j and &5 which leads toward the production of octannulate 

 somites. A trace of this is indicated in some of the somites of the 

 type specimen' as is shown in the figures. 



The remaining pre-anal somites XXVI and XXVII are typically 

 triannulate. Two post-anal annuli are present in the type and four 

 in the new specimen. 



A few anatomical facts gleaned from the Lake Pepin specimen, 

 though very fragmentary, are nevertheless of great interest ; for it 

 will be seen that in all essentials the alimentary canal is constructed 

 on the plan prevalent in the GlossipJwnidce. The position of the 

 mouth at the extreme anterior margin of the oral sucker in somite II, 

 or perhaps even in I, is paralleled in the Ichthyobdellidcs only in Not- 

 ostomum (Levinsen 1881). The probscis is long and slender, reach- 

 ing when retracted, from VI to X, at its posterior and receiving ap- 

 parently three pairs of slender ducts from the salivary glands., The 

 latter consist of very numerous small gland cells scattered diffusely 

 all through the preclitellal somites as far as the head. The oesophagus 



