42 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
stagnalis more closely than those of any other species (compare Figures 1 
and 27). 
The crop (i’glv., Figure 27), as in G. stagnalis, bears a single pair of diver- 
ticula, which arise in the middle of somite xrx.; but the diverticula are 
shorter in this species than in stagnalis, ending usually in somite xx. (com- 
pare Figures 1 and 27). The stomach (ga.), as in all species of Glossiphonia, 
bears four pairs of lateral diverticula. They arise within the three somites 
xx.-xxu. All are directed slightly forward. The intestine (in.) is a simple 
tube not constricted into distinct chambers proximally as in most species. 
The anus (an., Figure 24) lies just behind somite xxv. 
In the structure of its digestive tract, as well as in the composition of its 
somites, this species shows a more reduced, simpler condition than is found 
in any other species known to me, stagnalis coming nearest to it in these 
particulars. 
e. NERVOUS SYSTEM. 
On account of the transparency of the body the central nervous system can 
be studied with ease in this species, either in the living animal or in whole 
preparations. In the ventral ganglionic chain there are, as in all species of 
Glossiphonia, twenty-one distinct ganglia. These innervate somites VIL.—XxXVII. 
respectively. 
The brain (cb., Figures 23, 27; also Figures 25, 26) represents the fused 
ganglia of the first six somites. The arrangement of its ganglionic capsules 
is the same as in G. stagnalis and G. fusca (Figures 8, 10, 12, 18). The two 
ventral capsules of somite vi. (6, 6, Figure 25) are arranged tandem, those of 
somites I.—-v., side by side. The supra-cesophageal commissure lies well back, 
about over the lateral capsules of somite v. (Figure 26). 
4. Glossiphonia heteroclita Lixyyzvs (1761). 
Plate 5; Plate 8, Figs. 35, 36, 38. 
Hirudo heteroclita Linneus (1761); H. hyalina O. F. Miiller (1774); Clepsine 
hyalina Moquin-Tandon (’26). . 
a. Hasitat, Form, S1ze, Conor. 
This small and transparent leech is found both in Europe and in North 
America. Compared with G. stagnalis and G. fusca, it has a proportionally 
shorter and broader body (Plate 5, Figures 19, 22 ; Plate 8, Figure 38. Com- 
pare Plate 1, Figure 1; Plate 2, Figure 4) ; in its movements, it is less active. 
It is found in ponds and sluggish streams, such as G. stagnalis frequents. 
Length of largest individuals, when extended, 13 mm. ; at rest, 8-9.5 mm. 
7idth, extended, 3 mm.; at rest, 4.25 mm. 
Color. — The body is in general very clear and transparent, like that of a 
jelly-fish, but shows great individual variation in the matter of pigmentation. 
First, it always has more or less of a golden-yellow tint caused by the pres- 
