NOTES AND MEMORANDA, 163 
Medusa undergoes when transferred to brine of saturated 
strength. 
If, then, we desire to draw any comparison at all, and if there 
is anything “astonishing” in the fact that a quickly fatal issue 
follows in the one case, while no harm results in the other, I 
should, nevertheless, still prefer adhering to the unit fixed by 
physiological conditions rather than to that supplied by chemical 
analysis. 
In the same note of the ‘Quarterly Journal of Microscopical 
Science’ there appears a very interesting statement by Mr. 
Moseley, and another by Professor Agassiz, regarding the occur- 
rence of marine Medusz in ‘‘ quite brackish,” or even “almost 
fresh,” water. One remark made by Professor Agassiz in this 
connection appears to demand some notice from me. He says: 
“So far as my experience goes, it is not conclusive of so fatal 
an action of fresh water on Medusze as Romanes would lead us 
to believe in,” &c., proceeding to relate his own observations on 
sundry species of Medusze which live in the estuary of the Charles 
River. Now, as Professor Agassiz must have failed to refer to 
the observations which he thus appears to stigmatise as inaccu- 
rate, I will ask you to be kind enough, for his information, to 
quote them in extenso. For this purpose I give below an 
extract from the ‘Philosophical Transactions? in which they 
occur, and from which it will be seen that I have made no 
experiments or statements with reference to the effects of brackish 
water, either in estuaries or elsewhere. My experiments con- 
sisted merely in svddenly transferring Medusz from sea water 
to perfectly fresh water. It certainly does surprise me to 
learn that Sarsia, Tiaropsis, and Aurelia are able to thrive 
in water tha} “tastes but little of salt ;” but the fact in no 
way touches any of my published results. I can only con- 
clude from it that a gradual transition from salt to comparatively 
fresh water not giving rise to such rapid osmosis is not so in- 
jurious to Medusz as I should have expected from the morbid 
effects of sudden transition. The whole subject is thus shown 
well worthy of further experimental inquiry; but, so far, the 
following are the only experiments that I have conducted with 
reference to it.—GzorcE J. RoMANEs. 
Extract from ‘ Phil. Trans.,’ vol. 167, p. 744. 
As fresh water exerts a very deadly influence on the 
Medusz, this seems the most appropriate place for describing 
its action. Such a description has already been given by 
Professor L. Agassiz, but it is erroneous. He writes: “Taking 
up ina spoonful of sea water a fresh Sarsia in full activity, when 
swimming most energetically, and emptying it into a tumbler full 
