-48 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 



Each of the white spots in the paired rows contains an inconspicuous, low 

 rounded papilla (much less prominent than are the papiUse of G. complanata, 

 so far as my observations go). 



The median row of white spots is less well developed than are the paired 

 rows ; in the four or five somites immediately anterior to the anus, it is com- 

 monly replaced by a continuous, median, clear vitta, within which is seen a 

 narrower band of the lemon-yellow reserve-food cells. 



Obviously the color pattern of this species resembles very closely that of G. fusca, 

 although in a majority of characters the animal is more closely related to G. 

 parasitica. 



b. Surface, Rings, Somites, Eyes, Suckers. 



The surface of the body is rather rough, owing to the strong development in 

 this species of the integumental sense-organs described by Bayer ('98). It 

 does not, however, bear conspicuous papillae, as is the case with G. parasitica 

 and the European G. complanata. The low, rounded papillae which are 

 found in the paired longitudinal rows of white spots are much smaller than 

 the similarly placed papillae of G. complanata. In this particular G. elegans 

 seems to agree with G. coucolor (see Apathy, '88, page 771). 



External rings, as a rule, rounded and distinct, less convex and not pointed as 

 are those of G. complanata, sixty-eight in number, distributed as follows : — 



Somites l.-iv. uniannulate ; but the boundary between rings 1 and 2 is often 

 inconspicuous (compare Figures 28, 29, 30), approaching the condition found 

 in G. stagnalis, where somites I. and ii. form a single broad ring, which, how- 

 ever, is sometimes divided by a shallow transverse furrow (Figures 3, 7). 



Somites v.-xxiv. triannulate, but the condition of somite v. is peculiar. Its 

 anterior annulus (5, Plate 7, Figures 28-31) is commonly narrow and imper- 

 fectly separated from the following (sensory) annulus (6). This case illus- 

 trates well the initial step in reduction (or final stop in elaboration, p. 33) 

 of the triannulate somite. It represents an intermediate stage between the 

 biannulate and triannulate condition of somite v. seen respectively in G. stag- 

 nalis (Figure 7, Plate 3) and G. heteroclita (Figure 20, Plate 5). 



Somite xxv. is biannulate (Figure 28), but the furrow between its two annuli 

 is often inconspicuous. Somites xxvi. and xxvii. are commonly uniannulate, 

 though notched at the margin of the body, which fact shows that the final step 

 in somite reduction (or initial step in somite growth) is not yet accompUshed 

 in the case of these somites. 



Eyes, six, in two parallel rows close together, in rings 3 and 4 (Figure 30). 

 Sometimes the first pair of eyes Lies partly in the posterior half of ring 2 

 (Figure 29). The middle pair is the lat-gest of the three ; the anterior pair, 

 the smallest. The first two pairs are directed obliquely forward, the last pair 

 obliquely backward; all are turned away from the median plane (Figures 29, 

 30). From the relation of the eyes to the nerves connected witli tlie metarneric 

 sensillse (Figure 29), it is plain that the three pairs of eyes have been derived 

 from the sensillse of somites ii., iii., and iv. respectively. It is further evi- 



