7 8 THE LEECHES OF MINNESOTA 



times the width of G. nepheloidea and much more flattened, but 

 still decidedly convex above. The head is small but moderately 

 distinct, less elongated and more strongly annulated than in G. 

 nepheloidea. The caudal sucker is well developed, strongly directed 

 ventrad, and but little exposed posteriorly ; its axis ordinarily at 

 about right angles to the body axis. While only one pair, situated 

 as in G. nepheloidea, the eyes are much more conspicuous owing to 

 the greater amount of their pigment, A conspicuous feature is the 

 more or less deep brown chitinoid plate and underlying gland situ- 

 ated on the dorsum of VIII ai and as. 



There are no distinct integumental papillae though the surface 

 may be somewhat roughened with scattered sense organs. The 

 metameric sensillae are inconspicuous as in G. nepheloidea. 



The annulation is distinct throughout, especially at the caudal 

 end, where the annuli are angulated at the margins. Somites I and 

 II are usually completely united in the short prostomium ; III is 

 uniannulate or occassionally faintly subdivided ; IV and V are bian- 

 nulate, the latter more completely and sometimes showing indica- 

 tions on the dorsum of the furrow alias; VI to XXIV are triannu- 

 late, and XXV and XXVI biannulate, the latter occassionally being 

 united with XXVII, which is commonly represented by a pair of 

 wedged-shaped halves nearly sundered by the anus. 



The mouth is smaller but otherwise similar in form and position 

 to that of G. nepheloidea. Diffuse salivary glands extend through 

 somites XII to XIV or sometimes farther. Never more than six 

 pairs of gastric caeca are present, but the number is variable and 

 may be reduced to three pairs by the obliteration of the first three. 

 All are simple and unbranched and increase in size from the first 

 to the sixth pair, the last being much the largest and reflexed caudad 

 through three or four somites (XIX to XXII). 



The external genital orifices and the reproductive organs gen- 

 erally are essentially like those of G. nepheloidea. The longitudinal 

 muscle cells are arranged diffusely but are strongly developed. 



Tale gray, pink, brownish or greenish tints, which are much 

 affected by the contents of the alimentary canal seen through the 

 more or less translucent tissues, arc the colors of this species. 

 Young specimens and some adults arc almost colorless and trans- 

 lucent, but commonly the tissues of the larger ones are rendered 

 opaque by the presence of numerous reserve and pigment cells. 



