50 BULLETIN : MUSEUM OF COMPAEATIVE ZOOLOGY. 



The proboscis (pr'b., Figure 28) is long, extending over somites viii.-xii. 

 There is practically no oesophagus, as I have used the term, for the pharyngeal 

 sac containing the proboscis extends back almost to the beginning of the crop. 



The salivary glands are numerous, often reaching seventy-five or more in 

 number in each half of the body. They are scattered usually through somites 

 xi.-xviii. In Figure 28 they are represented as relatively a little too small. 



The crop (i^glv.) bears seven pairs of large, lateral diverticula directed back- 

 ward and often lobed distally. They arise in somites xiii.-xix., always in the 

 middle of a somite, as in the other species described. The last pair of crop 

 diverticula is, as usual, the largest of all ; it may extend back through three or 

 four somites, giving off secondary lateral diverticula metamerically, as shown 

 in Figure 28. Often, however, when the crop is empty, the last pair of diver- 

 ticula is little longer than the preceding pair. 



The stomach (ga., Figure 28) bears, as in other species, four pairs of diverti- 

 cula, which arise within the three somites xix.-xxi. The intestine (in.) extends 

 through the six remaining somites, consisting proximally of two distinct cham- 

 bers limited by valve-like constrictions and usually situated in somites xxil. 

 and XXIII. Distally it is a gradually narrowing tube terminating at the anus 

 just behind somite xxvii. 



e. Nephropores, Nervous System. 



The nephropores open ventro-laterally, a little anterior to the middle of the 

 sensory ring of a somite. The number of nephridia has not been determined 

 for this species. 



The hrain {cb., Figures 28, 30) lies for the most part in somite vii. The 

 arrangement of its ganglionic capsules (Figure 5, Plate 2 ; Figure 11, Plate 3) 

 is usually similar to that found in the brain of G. stagnalis and G. fusca, but 

 the capsules are not so closely crowded together, and the supra-cesophageal com- 

 missure lies well forward, not being carried back over the middle of the brain 

 as in G. stagnalis (Figure 12). The less crowded condition of the capsules in 

 this species (Figure 5) explains an abnormality in their arrangement observed 

 in the brain of a single individual out of several examined; the two ventral 

 capsules of somite iii. (usually found side by side as in G. stagnalis and the 

 other species already described) were in this case arranged tandem, just as ill 

 ganglia in unabbreviated somites. 



Comparing the conditions of the brain capsules in the several species described 

 in this paper, one may say that the larger the leech is, the less are its capsules 

 crowded. This fact seems to indicate that the capsules, and probably the indi- 

 vidual ganglion cells also, do not increase in size proportionally with the growth 

 of the leech. This is certainly true of the development of the individual, if not 

 also of the race, for in the very young leech the ganglia of the nerve chain oc- 

 cur in close succession with scarcely any intervening space, whereas in the adult 

 they may be separated by a distance of two rings or even more. 



