124 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY, 



have become characteristic of jellyfishes, and result from their mode of 

 hfe and the simplicity of their structure. Their repetition in closely 

 allied genera may denote structural affinity, while in distantly allied 

 groups it may be the I'esult of mechanical combinations, and in no way 

 indicate any affinit}'. 



The four primary segments of Eucope are of uniform size in the ma- 

 jority of the specimens examined. Whenever there is suppression of a 

 radial canal, as in the case of specimens with three radial canals, the 

 segments are sometimes uniform (Plate III. Figs, 3, 6), or one of the 

 segments, as in Plate III. Fig. 1, is nearly 180°, indicating the total sup- 

 pression of the fourth radial canal at its normal point of development. 

 See also Plate III. Fig. 4, in which one of the segments is smaller than 

 the two from which the fourth section has been cut. 



The inequalities which exist in the segments of some of the specimens 

 can best be expressed by a table : — 



1- 1- 1..^?. 1- i-^i- ?; ?._ 1- 6. 2^5. 

 •■■J •*• > •'^1 1 > ^ > ^ » ^^ '11' '1' 1' 



1- 1- 1- 1 — 1-^ l-^-l- ^-l-^--l- ^-l- ^ — 1- ?• ?•? 

 1. i, i, 1, i, J, i. J, i, i^^'i' i. !• i. J. i. 1' i-i 



1; 1; 1; 1; 1;-1; -; p jjfs-l; Ij 1; 1; 1? 



L52^2^2^_ ^ ^ ^ ^ _. 3^44 3.5 

 • 1 ' 1 ' 1 ' 1 ' ' 1 ' 1 ' 1 ' 1 ' ' 1 ' 1' 1' T' 



~^~~ 2 2 2 2 2 



1; !;_; _; _;_1; -• 1; 1" =• 

 ' ' 1 1 1' ' 1' ' ' 1' 



The — " — . indicates a fork of the radial canal. 



2^ 2 2 2 _ 2 1^ 2 1.5 1.5 2 2 2 2 



1, i^^'i'i'i' ^' !> i; I'rT' ' I'l'i'T'i' 



L5. L5. L7. L5. 1.5 



; 1 ' T' T' T' T' 



In this table 1 expresses the smallest segment ; the approximate 



2 

 dimensions of the others are represented by multiples of it thus : indi- 

 cates that a segment is twice as wide at the periphery as the smallest ; 



3 5 



~, that it is three and a half times as wide. Of course, the value of 1 



is a different value in each case. 



