568 Chas. W. Margin. 



As compared with the variations occurring in other organs, par- 

 ticularly the marginal organs and canals, the per cent is extremely 

 small, as will be seen at a glance in comparing the several tables. 

 My observations on this point confirm those of both Bateson and 

 Browne. The former found but 1.6 per cent, while the latter 

 found it as large as 2.4 per cent. My observations gave the average 

 of 2.75 per cent, as the total variations to be detected in Aurelia 

 flavidula. 



As already suggested in connection with Ehrenberg's observa- 

 tions, in which he claimed that variation reached 10 per cent, 

 either this must be taken to include the total, in which case it is 

 evidently too low, or if it refer to the vegetative organs alone it is 

 certainly too high, unless indeed it may be possible that the Aurelia 

 aurita of the Red Sea differs very greatly from the species in other 

 waters, or from our own species. 



Rhopalia and Radial Canals. 



An examination of the several tables will show that there is a 

 general variation in the direction of an increase in the number of 

 both rhopalia and radial canals. This has been shown to be the 

 case in Aurelia aurita by both Ballowitz {op. cit.), and Browne 

 (op. cit.). While confirming for the most part the results obtained 

 by both these observers, there are points of difference which 

 must be reviewed with some detail, and other points wherein 

 I am unable to accept the conclusions of either in all par- 

 ticulars. Some of these will be considered in their appropriate 

 connections. 



Concerning the number of rhopalia little need be said further 

 than to direct attention, as above, to the tabulated facts. A brief 

 word or two in explanation of the Tables V to VII will suffice to 

 render their meaning clear. Beginning with the first, or left hand 

 column, there is listed the number of specimens having the 

 characters given in the following columns. For example, in the 

 second is given the number of gastric pouches, or lobes, in the 

 third the number of oral lobes, in the fourth the number of 

 rhopalia, and finally in the last the canal system not including 

 the adradial system, since it bears for the most part, no direct 

 relation to the rhopalia. The numbers following in each case 

 refer to that of the rhopalia, and where less than the normal 



