VARIATION IN THE JELLY-FISH AURELIA AURITA 29 



diameter. It had 16 tentaculocysts, 8 perradial and 8 inter- 

 radial canals. It will be observed that 12 individuals or 

 4.3 per cent had an abnormal number of gonads, and that 

 where departure from the normal occurs the numbers tend to 

 be higher. This percentage is high when compared with 

 percentages which I have previously noted (I.e. p. 133), and 

 by way of explanation it is suggested (i) that too few 

 individuals are considered in this case, and (2) that there is 

 great difficulty in collecting nearly three hundred individuals 

 as they drift past a small boat without selecting, it may be 

 unconsciously, the very specimens whose gonads are seen 

 to be abnormal in number. 



Other details were noted, but since in connection with 

 them there is more likelihood that errror may arise from 

 insufficiency of specimens and unconscious selection in 

 collecting, it is not proposed to discuss them. The main 

 purpose I have is rather to direct the attention of readers of 

 the " Annals " to an aspect of biology in which some of them, 

 having peculiar facilities, might be able to supply useful 

 statistics. 



ZOOLOGICAL LABORATORY, 



UNIVERSITY OF EDINBURGH. 



CONTRIBUTION TO OUR KNOWLEDGE OF THE 

 HYDROID FAUNA OF THE WEST OF SCOT- 

 LAND. 



BEING AN ACCOUNT OF COLLECTIONS MADE 

 BY SIR JOHN MURRAY, K.C.B., ON S.Y. "MEDUSA." 



By JAMES RITCHIE, M.A., B.Sc., 



The Royal Scottish Museum. 

 (Continued from p. 225, No. 76, October 1910.) 



CALYPTOBLASTEA. 



Family HALECID^E. 

 15. HALECIUM BEANII, Johnston. 



CLYDE SEA AREA. DUNOON BASIN (M.) 20-40 fms. ; E. side, 

 5-10 fms., r. BARRIER PLATEAU Sanda to Achinhoan, 22 fms., 



