MISCELLANEA. 
I. Variability, Symmetry and Fertility in an abnormal Species. 
In the jelly-fishes of the group Hydromedusse four may he said to be the nonnal number of 
radii. There are ordinarily four radial canals, lips and gonads 90° apart. Pseudoclytia pentata 
(Mayer) differs from all other Hydromedusae in that it normally has 5 radial canals, 5 lips and 
5 gonads, 72° apart. The species occurs in great numbers at the Tortugas, Florida. We may 
speak of it as an "abnormal" species. In the Science Bulletin of the Brooklyn Museum, Vol. i. 
No. 1, Dr A. G. Mayer has given an interesting account of the variation of this species. The 
frequency of the different numbers of radial canals and of lips is given as follows : 
Frequency. 
1 
2 
3 
5 
6 
7 
s 
Radial canals ... 
1 
8 
56 
860 
64 
6 
1 
Lips 
2 
5 
18 
123 
798 
49 
1 
From the correlation table the following results have been determined by Miss M. Lewenz of 
University College, London : 
Organ 
Mean 
Standard 
Deviation 
Correlation 
Canals ... 
Lips 
5-004+ -009 
4-868 ±-01 2 
-4413 + -0067 
-5559 + -0084 
1 -3255 ±-0191 
The correlation between canals and lips is accordingly only moderate. 
The frequency distribution of lips has been specially dealt with by Professor K. Pearson in a 
" Supplement to a memoir on Skew Variation," Phil. Trans. A, Vol. 197, p. 456. It forms an 
illustration of one of the curve-types omitted in his original memoir on that subject. 
The individuals with 5 rays are nearly all radially symmetrical. The percentage of radially 
symmetrical individuals diminishes as we depart from this mode in either direction. In about 
two-thirds of the cases in which the canals have not a perfect radial symmetry they are neverthe- 
less bilaterally symmetrical. There is a strong inherent tendency for some sort of symmetry. 
Typically one gonad occurs on each radial canal, but one or more may fail to develop. Thus 
730 medusae with 5 canals had only 3080 gonads instead of the possible 3650. 
