AGASSIZ AND WOODAVORTH : VARIATIONS IN EUCOPE. 141 



In a specimen with only thi'ee radial canals, one of which forks above 

 the genitals, the formula is 



2,15,6,7; 3, 10,1; 9,2^,5,5; 



the otoliths being normal in numbei", but irregular in their distribution. 

 In another Eucope with three radial canals, we find seven otoliths 

 represented in the formula 



1, 11, 2; 4, 6, 5; 2,8,6, 7; 



the last sector being somewhat larger than the others. 



In a specimen with three equally developed sectors with the formula of 



12, U, 6; 6, 7, 10; 6, 7, 15; 



there are six otoliths, the normal number in each sector, but the other 

 marginal tentacles are most irregularly developed. 



In still another Eucope, similar to the preceding one, with three 

 sectors of equal size and well developed genitals with six otoliths, two 

 in each sector, the formula was 



10, 7, 10; 10, 9, 7; 9, 7, 8 ; 



Finally, a Eucope with three quadrants of the same size had only 

 three otoliths ; its formula is 



9, 6, 9 ; 27 ; 8, 9 ; 



The formation of spurs (Plate VIII. Figs. 4-13) takes place usually 

 at the base of the marginal tentacle, at its connection with the circular 

 canal, but cases have been observed in which the spur shoots off from 

 the lash of the tentacle (Plate VIII. Fig. 5). The formation of spurs 

 is often accompanied by the atrophy of the inframarginal knob of the 

 marginal tentacles (compare Plate VIII. Figs. 9-13, with Figs. 4-8). 



It will be noticed that in the numerical variation of the segments the 

 tendency is not to doubling the number of normal (4) segments, but 

 either to add one or two, or to reduce the segments to three. 



In Sarsia, Agassiz observed a specimen with six radial canals and 

 Romanes one with five ; he also observed a Sarsia with six radial canals, 

 six ocelli, and six tentacles, like that seen by Agassiz, the only speci- 

 men in thousands examined. 



According to Bateson, the numerical variations in Aurelia tend in two 

 directions, i. e. to forms with six and twelve segments instead of the 

 normal eight. 



The same tendency in Aurelia to vary in the direction of six and 



