Variation in Aurelia aurita. 



133 



genital sacs and a decreased number of tentaculocysts. Although my observa- 

 tions are that an abnormal number of gonads is in every case accompanied 

 by an abnormal number of tentaculocysts and unbranched radial canals (the 

 converse is not true), Browne (op. cit., p. 107) detected four examples (in 3000) 

 with eight tentaculocysts and an abnormal number (3, 3, 5, 8) of genital 

 sacs. It has further to be noted, from Table III., that the range of gonads is 

 from 2 to 6, the number of tentaculocysts from 4 to 14, and that as regards 

 the branched canal system, the perradials range from 2 to 8 and the inter- 

 radials from 2 to 6. 



Table IV. 



Comparative, Table of Adults with an Abnormal number of Gonads. 



Authority . . 



M'Intosh. 



Browne. 



Bateson. 



Hargitt. 



Locality .... 



Clyde. 



Plymouth. 



Northumberland . 



Wood's Hole. 



Number of Specimens \ 



examined . . J 

 Range of number of\ 



Gonads . . . J 

 P.c. with decrease in\ 



number of Gonads . J 

 P.c. with increase in"! 



number of Gonads . J 



1000 

 2-6 

 0-2 

 1-6 



3000 



2-10 



0-6 



1-8 



1763 

 2-6 



0-62 

 0-85 



2500 



' 2-6 



0-56 



2-20 



Total p.c. Abnormal 



1-8 



2-4 



1-47 



276 



In Table IV. there are given comparative lists showing the number of 

 specimens with an abnormal number of genital sacs. These lists are remark- 

 ably consistent in showing that for A. aurita (for Hargitt thinks A. flavidula 

 is identical with A. aurita) — (1) there is but a small variation in the number 

 of gonads (on an average about 2 per cent.) ; and (2) such variation as does 

 occur is towards an increase in the number of gonads. 



3. Variations in the Number of Oral Lobes. 



Columns 2 and 3 of Table III. show the interesting fact that in every one 

 of my specimens where there is an abnormal number of gonads, there is the 

 same abnormal number of oral lobes. This corroborates Browne, who says 

 (op. cit., p. 107) — " There is a perfect correlation between the number of 

 genital sacs and the number of oral arms, and I have not found any ex- 

 ceptions ; a specimen with six genital sacs has always six oral arms." On 

 the other hand, I find that Hargitt records a few ephyrse of A. flavidula 



