734 
ME. G. J. EOMANES ON THE LOCOMOTOE SYSTEM OE MEDUSAS. 
specimens this effect is sometimes only observable, or best observable, at the commence- 
ment of a swimming-bout ; for in such specimens, after a greater or less number of unco- 
ordinated contractions, the four quadrants begin to agree, as it were, upon their rhythm. 
This, of course, is what might be expected on the above hypothesis regarding con- 
tractile waves eliciting ganglionic discharges, and all the ganglia requiring about the 
same time for their nutrition ; and the reason why the loss of coordination under this 
form of section is more marked in the discophorous species of naked-eyed Medusae than 
in Sarsia, is doubtless merely because the passage of contractile waves is so much more 
slow and so much less energetic. Therefore in vigorous specimens, where these waves 
pass more readily, we obtain results under this form of section most conformable to those 
which we obtain in Sarsia , viz. a sort of fictitious coordination which begins to come on 
after a variable number of contractions have been given, and which, as just stated, is 
doubtless due to the fact of all the marginal ganglia requiring the same time for their 
recovery from the exhaustion consequent on the occurrence of each discharge. 
(d) It is a remarkable thing that this form of section, although in actual amount 
so very slight, is attended with a much more pernicious influence on the vitality of the 
organism than is any amount of section of the general contractile tissues. Thus if a 
specimen of Tiarojosis, for example, be chosen which is swimming about with the 
utmost vigour, and if four equidistant radial cuts only just long enough to sever the 
marginal canal be made, the animal will soon begin to show symptoms of enfeeblement, 
and within an hour or two after the operation will probably have ceased its swimming- 
motions altogether. The animal, however, is not actually dead ; for if, while lying- 
motionless at the bottom of the vessel, it be gently stimulated, it will respond with a 
spasm as usual, and perhaps immediately afterwards give a short and feeble bout of swim- 
ming. These surprisingly pernicious results are not so conspicuous in the case of Sarsia , 
although in this genus likewise they are sufficiently well marked to be unmistakable. 
I here append a Table to show the comparative effects of the operation in question 
on different species. The cases may be regarded as very usual ones, though it often 
happens that a longer time after the operation must elapse before the enfeebling effects 
become so pronounced. 
1 
Name of species. 
Number of con- 
tractions during 
five minutes be- 
fore operation. 
1 
Number during 
one minute after, 
operation. 
Number during 
five minutes after 
operation. 
Ultimate effects. 
Tiaropsis diademata 
57 
11 
0 
Permanent rest. 
indicans 
148 
23 
0 
polydiademata 
102 
18 
0 
■ 
oligoplocama 
131 
39 
0 
Sarsia tubulosa 
1 
144 
56 
14 
” 
This decided effect of so slight a mutilation will not perhaps appear to other physiolo- 
gists so noteworthy as it appears to me ; for no one who has not witnessed the experi- 
ments can form an adequate idea of the amount of mutilation of any parts, other than 
