CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA. 49 
dent that the single pair of eyes found in each of the species stagnalis, fusca, 
and elongata corresponds with the middle (largest) pair of eyes of this species, 
the pair belonging to somite III. 
The oral sucker, as in the other species described, lies within somites I.-Iv. 
(Figures 29, 31). 
c. REPRODUCTIVE ORGANS. 
Male genital pore (po. @, Figure 28), between somites XI. and XII. (rings 25 
and 26), a position one ring anterior to that of the same structure in the 
species already described. 
Female genital pore (po. 9, Figure 28), between the second and third rings 
of somite XII. (rings 27 and 28), the usual position of this structure in the 
genus. 
Testes (te., Figure 28), ten pairs. The anterior six pairs occupy the same 
positions as the testes in the species already described, being placed interseg- 
mentally in somites — — . The remaining four pairs occur immediately 
behind those already mentioned ; the most anterior one, between the last 
crop and first stomach diverticulum, in somites = *; the other three between 
successive stomach diverticula, and like them separated by rather less than 
metameric intervals. No other species of Glossiphonia known to me, except 
the European G. complanata, has normally a greater number of testes than six 
pairs. In that species likewise the testes number ten pairs placed exactly as 
in elegans. This is one of several facts showing the very close relationship of 
the two species named. The last one or two pairs of testes are less constant in 
their occurrence than those farther forward. 
Eggs are laid by G. elegans, in the vicinity of Cambridge, in April, May, or 
as late as June. The temperature of the water in the spring undoubtedly 
exercises considerable influence in determining the time of egg-laying.  Indi- 
viduals brought into the laboratory on March 27, 1898, laid eggs nine days 
later. On April 29, 1900, animals of this species bearing eggs were collected 
from Alewife Brook, Cambridge, though G. stagnalis, found with them, appar- 
ently had not yet laid its eggs. The eggs are dull pinkish white in color and are 
borne on the under side of the body in from three to six large clusters, which 
are rather easily detached from the body, if the animal is disturbed. Each 
cluster contains a considerable number of eggs, often as many as twenty or 
twenty-five, enclosed in a delicate sac. The sacs are not arranged sym- 
metrically in two parallel rows, as in G. stagnalis and G. fusca, but quite 
irregularly, a sac being attached either in the median plane of the body or to 
one side of it, as the case may be. 
d. Digestive TRACT. 
The mouth is situated well forward in somite 111., anterior to the eyes, or at 
least anterior to the last two pairs of eyes (Figures 29, 31). 
