AGASSIZ AND WOODWORTH: VARIATIONS IN EUCOPE. 125 
1; 1; 1; is the formula for the segments of a Eucope in which they 
are of equal size, the radial canals forming an angle of 120? at the 
centre. 
1; 1; 1; 1; and 1; 1; 1; 1; 1; would each denote the formula 
for segments of equal dimensions in a Eucope with four and one with 
five segments. 
The formation of additional radial tubes may be due to the growth 
of independent tubes from the pouch at the base of the digestive cav- 
ity, or from the forking of tubes, the new canals eventually reaching 
the marginal canal. In one case we observed a radial canal which 
had its origin at the periphery and did not extend to the base of the 
manubrium (Plate VIII. Fig. 19). Such a formation of a new radial 
canal from the circular canal suggests a similar structure in the short 
canals, in which are found olusters of lasso cells extending at right 
angles from the periphery between the primary radial canals of Willia, 
and perhaps other Medus, in which we have clusters of lasso cells 
extending a short distance on the outer surface of the umbrella from the 
marginal canal. 
In the great majority of the specimens of Eucope observed, the 
radial canals are tubes with walls nearly parallel all the way from the 
base of the digestive cavity to the marginal canal (Plates I.-VI.). But 
in a great many instances this parallellism does not exist, and we find on 
the edge of some of the radial canals slight serrations, as in Plate VII. 
Figs. 1-4 and 6. These serrations vary greatly in size, and in some 
cases become short spurs (Plate II. Fig. 4, Plate III. Fig. 3, Plate VII. 
Figs. 2, 3, 5, 7), or even spurs of considerable length (Plate VII. 
Figs. 6, 9, 10); the longer spurs becoming often the forks of the 
primary radial canals (Plate III. Figs. 1, 2-5, Plate VI. Figs. 1, 2, 
Plate VII. Fig. 5), either above or below the genital pouches. Or the 
spurs may form connecting canals between the radial tubes (Plate VII. 
Fig. 4, Plate VIII. Fig. 20), or a rudimentary circular canal round the 
base of the manubrium (Plate VII. Fig. 8). 
Starting with the normal state, in which the genitals are equally 
developed, we find five or six variations, which cover by far the greater 
number of the specimens examined. 
The greatest number of the specimens (622 out of 1146) examined 
for variations in the genital organs were normal, the four genitals being 
equally developed ; the females were more numerous than the males; 
of the latter there were 175, and of the former 447. This stage is 
represented in the table by 1; 1; 1; 1; in which 1 means that the 
