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XVIII. Further Observations on the Locomotor System of Medusas. 
By George J. Komanes, M.A., F.L.S., &c. Communicated by Prof. Huxley, Sec. B.S. 
Received November 21, 1876, — Read January 11, 1877. 
[Plates 30 & 31.] 
In now submitting the second instalment of my observations on the locomotor system 
of Medusae to the consideration of this Society, I should like to preface the communi- 
cation with a few words to explain why several experiments which I had intended to 
perform this season have been unavoidably postponed. It is well known to naturalists 
that, from causes which are not very well understood, the numbers of Medusae in the 
same localities are subject, in different years, to considerable variations. Now on the 
part of the coast where my work has throughout been carried on — viz. the Cromarty 
Firth, on the east of Scotland — the Medusae have been this year as scarce as last year 
they were abundant. Probably the cause of this scarcity in the land-locked position 
occupied by the Cromarty Firth is in part to be attributed to the unusual prevalence 
of westerly winds which has this year been observable in that locality. But whatever 
the cause, the fact of this scarcity having existed has compelled me this year to restrict 
my observations, almost exclusively, to the genera Sarsia, Tiaropsis, and Aurelia. By 
way of introduction it is only necessary further to state that, for the sake of facilitating 
reference, I shall endeavour to construct the present communication on as nearly as 
possible the same general plan as the last one. 
I. FUNDAMENTAL OBSERVATIONS. 
§ 1. Effects of excising the entire margins of Nectocalyces. — Under this heading I 
have very little to add to the statements contained in my former paper. Many of the 
experiments which I have this year performed have necessitated, in a vast number of 
instances, the removal of the extreme periphery of nectocalyces ; and in no one instance 
I have I found an occurrence of even the slightest deviation from the general rule previ- 
ously enunciated — the rule, namely, that “ excision of the extreme margin of a necto- 
calyx causes immediate, total, and permanent paralysis of the entire organ”*. 
§ 2. Effects of excising the litliocysts from Gonocalyces ( Umbrellas ). — It will be remem- 
* I may here mention, what perhaps I ought to have mentioned in my former paper, viz. that, in the case 
of the species Tiaropsis diademata , it frequently happens that a single quadrant of the thus mutilated necto- 
calyx bends slightly inwards at long intervals and without rhythm. I may also mention that I have this year 
performed the fundamental experiment on three additional species of the genus Thaumantias , viz. T. pwrpureus 
(Porbes), T. crucifera (Romanes), and T. Tielicobostrica (Romanes). 
MDCCCLXXVII. 5 A 
