Variation in Aurelia aurila. 125 



XVI.— Variation in Aurelia aurita. By D. C. M'Intosh, M.A., B.Sc, 



F.R.S.E. (From the Zoological Department, University of Edinburgh.) 



(Read 22nd March 1909. Received 5th May 1910.) 



The main purpose of this research, suggested by Mr E. T. Browne, is to 

 ascertain whether forms of Aurelia aurita (Linn.) from the Clyde exhibit 

 as many deviations from the normal type as have been found in this, or in 

 closely allied, species from other areas. It has long been known that this 

 is one of the most variable species of Scyphomedusse. The obviously 

 symmetrical appearance of a normal specimen, the definite number of certain 

 important organs, the readiness with which, as a rule, any increase or 

 decrease in these numbers can be detected, as well as the ease with which 

 large numbers of this jelly-fish may often be collected, doubtless, to some 

 extent at least, explain the fact that it has formed the subject of several 

 important researches on variation. It is neither necessary nor desirable to 

 review here in detail the results of these observations, for very satisfactory 

 reviews of previous researches treating of variation in Medusae, and 

 especially in Aurelia aurita, and also references to literature, are given by 

 Ballowitz 1 up till 1898, and by Mayer 2 up till 1901. Since then, important 

 contributions to this subject have been made by Browne 3 and by Hargitt. 4 



Material. 



The original intention of the writer was to collect in the spring of 

 the year over a thousand specimens of Aurelia aurita in the Ephyra stage, 

 and to return to the same neighbourhood in the summer and collect an 

 equal number of adults, presumably of the same race. Thus it was proposed 

 to ascertain not only how Clyde forms varied as compared with forms from 

 other areas, but also to find to what extent, if at all, abnornal ephyrse 

 are handicapped in the struggle for existence. Circumstances, however, 

 made it impossible for me to get to the West of Scotland Marine 

 Biological Station till the middle of April, and it was on 20th April that 



1 Ballowitz, E., 1898, "Ueber Hypomerie und Hypermerie bei Aurelia aurita," 

 Archiv. fur Entwich. der Organismen, Bd. viii., pp. 239-252. 



2 Mayer, A. G., 1901 (April), "The Variations of a Newly-arisen Species of 

 Medusa " : The Museum of the Brooklyn Institute of Arts and Sciences, Science Bulletin, 

 vol. i., No. 1, pp. 1-27 (two plates, 67 figs.). 



3 Browne, E. T., 1901 (October), "Variation in Aurelia aurita," Biometrilca, vol. i. 

 pp. 90-108 (three text-figs.). 



4 Hargitt, C. W., 1905. " Variations among Scyphomedusa?," The Journal of 

 Experimental Zoology, Baltimore, vol. ii. pp. 547-582 (one plate and 17 text-figs.). 



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