128 Proceedings of the Royal Physical Society. 



radial canals may be distinctly seen on examining each individual with 

 a lens. The variations noted consist (a) in the amount of increase or 

 decrease in the number of (1) Tentaculocysts, (2) Genital sacs and gonads, 

 (3) Oral lobes, (4) Branched radial canals : (b) in the occurrence of forms 

 showing change in the number of certain parts, the organism being 

 sometimes radially symmetrical, sometimes bilaterally symmetrical, and 

 sometimes asymmetrical. Comparative tables are also given showing 

 to what extent the observations made on specimens from the sheltered 

 waters of the Clyde correspond with facts already recorded for individuals 

 of the same, or a closely allied, species from such different localities as 

 the Tamar, near Plymouth, 1 the coast of Northumberland,' 2 and from 

 near Wood's Hole, Mass. 3 The following is the record of my observations 

 on 1000 individuals : — 



1. Variations in the Number of Tentaculocysts. 



Table I. shows the variation in the number of tentaculocysts in the 

 specimens I examined. Browne collected 2000 small adults, varying from 

 10 to 40 mm., from the Tamar, near Plymouth, between 23rd and 27th April 

 1898. His specimens give an average umbrella diameter of about 18*8 mm., 

 whereas the ones I gathered on 20th April 1903, from the Clyde, are con- 

 siderably smaller, being on an average only about 12 - 3 mm. in diameter. 

 Growth is probably at that stage very rapid. Although Browne does not 

 specifically say so, it is possible from the tables he gives to show, that in 

 about five weeks, a race of Aurelia aurita grew from immature adults 

 (average diameter 18 - 8 mm.), just past the ephyra stage to a series with an 

 average diameter of almost 56 mm., and " most of the larger ones carried 

 planula; in the pouches on the oral arms, showing that they had reached 

 full maturity " {I.e., p. 93). 



But the main purpose of Table I. is to exhibit the variation found in the 

 number of tentaculocysts. This is seen to range from 4 to 16, and to 

 give a total variation of exactly 16 per cent., 2 - 2 per cent, having fewer 

 than and 13 - S per cent, having more than, the normal 8 tentaculocysts. 

 Prom the last column of Table I., it is seen that Browne finds (in 2000 

 immature adults) the number of tentaculocysts ranges from 4 to 15, and a 

 total variation of 20 '2 per cent. (4 - 5 per cent, showing a deficiency and 15 - 7 

 per cent, an excess). This is a greater variation than I found in the Clyde 



1 Browne, hi. T., op. cit. 



' Bateson, W., Materiahfor '/<■ Study </ Variation, pp. 123-429, London, 1894. 



1 Hafgitt, O. W,, op. cit. 



