Variation in Aurelia aurita. 



139 



It has already been remarked that the branching of the canal system 

 while essentially of one type, showed considerable variety (Fig. 1). Some- 

 times the lateral branches do not always start from the same point on the 

 main canal (Fig. 3). There is not always the same degree of separation 



Fig. 3. 

 Perradial canal {p.c.) with non-adjacent lateral branches (Lb. 1 and l.b. 2). 



between the genital sacs or the gonads, nor are they always of equal size. 

 Sometimes a gonad in its genital sac seems to have pushed its way outwards 

 towards the margin of the umbrella to such an extent that the base of the 

 interradial canal is entirely cut off, and the starting-point of the branching- 

 canal system is obliterated (Fig. 4). The result of this is that what was 

 undoubtedly originally a branched interradial canal becomes an unbranched 



Fig. 4. 



Example in which genital sac (with gonad) has advanced so far toward 

 the margin of the umbrella that the original main \ateral adjacent branch- 

 ing of the interradial canal system is obliterated. 



canal, stili of course retaining its interradial position and having its 

 tentaculocyst. As the tentacles, which fringe the margin of the umbrella, 

 are apt to become detached, their number was not systematically counted, 

 but sufficient note was taken to make it certain that the number between 

 two sets of adjacent tentaculocysts is not constant for a single individual, 



