AGASSIZ AND WOODWORTH : VARIATIOXS IX EUCOPE. 125 



1 ; 1 ; 1 ; is the fornmla 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 j 1 ; 1 j 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 i-eachiug 

 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 clusters of lasso cells extending at right 

 angles from the periphery between the. primary radial canals of Willia, 

 and perhaps other Medusae, 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 shoi't 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 



