36 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
6. Rives, Somires, Eyes, SucKERs. 
External rings, not quite so distinct as in G. stagnalis ; skin, slightly rougher 
owing to the stronger development of Bayer’s (96) sense organs. Number of 
preanal rings, seventy (Figure 13, Plate 4). 
Somites V.-XXIV. are triannulate, but the two anterior rings of v. are united 
ventrally (Figure 15). 
Somites I. and 1. are included in a single broad ring, which, just as in G. 
stagnalis, is sometimes subdivided by a shallow transverse furrow (Figure 14) 
marking the boundary between the two incompletely fused somites. 
Somites IIl., Iv., XXV. and xxvi. (Figures 13-16) are biannulate. In each 
case the broader, anterior ring bears the sensilla and corresponds to rings 1 and 
2 of triannulate somites (compare somites Iv. and v. of Figure 15). 
Somite XXVII. is a single broad ring (70, Figure 13) which lies just anterior 
to the anus, not crowded back of it, as in stagnalis (Figure 34, Plate 8). 
The principal differences in somite composition between fusca and stagnalis 
occur in the head region, in somites 111.—v. These somites are less abbreviated 
(or more fully elaborated) in fusca than in stagnalis, hence the greater number 
of preanal rings in the former (seventy) as compared with the latter (sixty- 
seven). 
Eyes, two, large and distinct, situated in rings 3 and 4 (Figures 14-16). 
The sensory elements of each eye, as in G. stagnalis, are contained in a pig- 
ment cup which is open only on its anterior, lateral surface, where the nerve 
fibres make their exit (Figures 14, 16). 
Oral sucker, as in all species of Glossiphonia, included within the first four 
somites (Figures 14, 15). 
Posterior sucker of about the same dimensions as in G. stagnalis, slightly 
longer than broad. 
c. REPRODUCTIVE ORGANS. 
Male genital pore (po. @, Figure 13), between the first and second rings of 
somite xII. (rings 27 and 28). 
Female genital pore (po. 9, Figure 13), between the second and third rings 
of somite XII. (rings 28 and 29). 
Testes (te., Figure 13), six pairs situated intersegmentally in somites 
XIII. XVIII. 
XIve) Suen 
The ovaries have the usual form and position of these structures in other 
species, being found ventrally in the median lacuna. 
Eggs are laid a month or six weeks later than by G. stagnalis (June 12, 
1898, Cambridge, Mass.). In color they resemble those of G. stagnalis closely, 
being of a light pink or flesh color. As in G. stagnalis, the eggs are attached 
to the under side of the body posterior to the genital pores, within a number 
of delicate sacs arranged in two parallel rows, close together, one on each side 
of the median plane. The number of sacs is most often six, but a seventh sac 
