308 



della Floridiana Verril 20 and Aulastomum gulo 10 — 15 denti- 

 cules. The largest wel! developed teeth have , as we saw, a conical 

 form , with two roots , resembliug the point of an arrow , the 

 small ones, which are lound at the internal angles of the jaw , 

 have ouly a conical form without roots. At the mediau angle of 

 the jaw , the denticules are less developed than more in the cen- 

 trum of the series , but only few have diminished in size , whilst 

 on the lateral angle a great number of teeth are reduced ; the 

 reduction begins already near the middle of the row, increasing 

 towards the angle, the last denticules being very small. 



Leuckart ') is wrong in saying that the median teeth are the 

 smal lest. 



The teeth of Hirudo are straight and not curved ; they are 

 placed perpendicularly on the convex edge of the jaw, one root 

 on eacb side. 



The connection of the teeth to the cuticula will be treated 

 when speking about the epithelium of the jaw. 



The central bundie of the glandducts is surrounded on both 

 sides by the muscular mass. This mass is composed of fibres 

 which are arranged in three directions. In addition to these other 

 fibres occur, which extend from one angle of the jaw to the 

 other, the transversal fibres mentioned above (t. s. in fig. 3, 4 

 and 11), which are longitudinally cut in sections as illustra- 

 ted in fig. 3 and 4. The third main direction of the muscular 

 fibres is paralel to those of the glandducts. 



These muscular fibres have the same histological structure as 

 those of the head; they touch the epithelial cells of the jaw. 



Of the transversal muscular fibres are to be seeu the nuclei in 

 my fig. 3 and 4 (ts). 



I have observed already, that these transversal muscular fibres 

 divide the bundie of glandducts in a number of secundary bund- 

 ies. Some glandducts do not follow the direction of the mainbundle, 

 but leave it to open on the side of the jaw. These glandducts 



1) Leuckart. Parasiten des Menschcn. p. 623- 



