VARIATION IN AURELIA AURITA. 
By EDWARD T. BROWNE. 
Zoological Research Laboratory, University College, London. 
In 1895 an article on the Variation of the Tentaculocysts of Aurelia aurita 
(Linn.), written by me, was published in the Qiairterly Journal of Microscopical 
Science. The chief object of the research, suggested by Professor Weldon, was 
the finding out the variation in the number of tentaculocysts, and if a variation 
occuri'ed among the Ephyrae to see how far it affected the adults. The material 
for that investigation was collected in Plymouth Sound by the officials of the 
Marine Biological Association in 1893 and 1894. The results showed that there 
was a considerable variation in the number of tentaculocysts. The number of 
tentaculocysts (marginal sense-organs) is definitely fixed in the larval stage, 
commonly known as an Ephyra. A normal Ephyra has eight marginal lobes, or 
arms, each with a terminal sense-organ (tentaculocyst), and a prolongation of the 
stomach, forming a canal, runs along the middle of each lobe to the sense-organ. 
A variation in the number of lobes affects also the number of tentaculocysts 
and the number of radial canals. The three are distinctly correlated, except when 
a twinning of the tentaculocysts occurs. This is very rare and only occurred five 
times in 1000 adult specimens. 
It is easy to detect cases of twinning in the adults but not in the larval 
Ephyrae. Occasionally an Ephyra is found having two tentaculocysts at the 
end of an arm and the canal bifurcated. In some specimens, no doubt, this is 
genuine twinning, but it is possible for the two tentaculocysts to become widely 
separated b}' the growth of the umbrella, and each to have its own canal system. 
I have, therefore, included twinning in the variation as it does not practically 
interfere with the results. 
It may be taken for granted, that, whatever number of tentaculocysts an 
Ephyra starts life with, that number remains constant during the whole life of that 
individual and that no further increase in number takes place during development. 
