Variation in Aurelia aurita. 



129 



examples. It is possible that the frequency of variation in the number of 

 tentaculocysts varies for groups of Aurelias from different localities. Browne 

 has already expressed the opinion, after an examination of 3000 specimens of 

 all sizes from the Tamar, where the variability in the number of tentaculo- 

 cysts is 21 per cent., that " the Tamar Aurelia may be safely regarded as a 

 local race " (I.e., p. 91). Further, it may very well be that this theory of 

 the existence of "local races" receives, indirectly, support from Hargitt 



Table I. 

 The Numerical Variation of the Tentaculocysts of '1000 Immature Adults. 



Diameter of the Umbrella in 



Millimetres. 





Percentage 



Percentage 









Total. 



for 1000 

 Clyde 



for 2000 

 Plymouth 



















10 



15 



20 



25 





Specimens. 



Specimens. 





4 



1 









1 



o-i 



0-05 



«3 



5 



1 







... 



1 



o-i 



o-i 



!>> 



6 



1 







: 



1 



o-i 



0-6 



o 



7 



15 



3 



1 





19 



1-9 



3-75 



a 



8 



548 



219 



67 



6 



840 



84-0 



79-8 



+3 



9 



16 



6 



3 



1 



26 



2-6 



5-75 



Eh 



10. 



24 



13 



3 



2 



42 



4-2 



4-55 



11 



10 



6 



2 





18 



1-8 



3-6 



c 



12 



18 



12 



2 





32 



3-2 



1-25 



a) 



13 



1 



4 



1 



... 



6 



0-6 



0-35 





14 



7 



3 







10 



1-0 



o-i 



fc 



15 





1 







1 



o-i 



o-i 



16 



1 



2 





... 



3 



0-3 





Totals, 



643 



269 



79 



9 



1000 



100 p.c. 



100 p.c 



(op. cit., p. 581), who finds that, after an examination of 2500 specimens of 

 Aurelia flavidula — very closely allied to A. aurita — 25 per cent, of those 

 from Wood's Hole show an abnormal number of tentaculocysts (the 

 deficiency being 2 per cent, and the excess 23 per cent.). 



A specially noteworthy feature of Table I. is seen in a comparison of 

 the percentage columns. Of specimens showing an excess (9, 10, etc.) in the 

 number of tentaculocysts, Browne's percentages read 575, 4 - 55, 3"6, T25, - 35, 

 OT, - l — a consistently decreasing series, in fact, just such a decreasing 

 series as one might expect as one departs further and further from the 

 normal type. On the other hand, the corresponding percentages of ab- 

 normality for Clyde specimens are 26, 4 - 2, T8, 3 - 2, - 6, TO, - l, 03 — giving 



