MR. Gf. J. ROMANES ON THE LOCOMOTOR SYSTEM OF MEDUSAE. 
735 
their margins, which the Medusae will endure without suffering even from the effects 
of shock. Another point worth mentioning with regard to the operation we are consi- 
dering is that not unfrequently the interruptions of the margin, which have been 
produced artificially, begin to extend themselves through the nectocalyx in a radial 
direction ; so that in some cases this organ becomes spontaneously segmented into four 
quadrants, which remain connected only by the apical tissue of the bell. I do not 
think that this is due to the mere mechanical tearing of the tissues as a consequence of 
the swimming motions, for the latter seem too feeble to admit of their producing such 
an effect. 
(e) In conclusion, I may state that I have been able temporarily to destroy the 
ganglionic coordination of Sarsia by submitting the animals to severe nervous shock. 
The method I employed to produce the' nervous shock without causing mutilation was 
to take the animal out of the water for a few seconds while I laid it on a small anvil, 
which I then struck violently with a hammer. On immediately afterwards restoring 
the Medusa to sea-water, spontaneity was found to have ceased, while irritability 
remained. After a time spontaneity began to return, and its first stages were marked 
by a complete want of coordination ; soon, however, coordination was again restored. 
But this experiment by no means invariably yielded the same result. Spontaneity, 
indeed, was invariably suspended for a time; but its first return was not invariably, or 
even generally, marked by an absence of coordination, even though I had previously 
struck the anvil a number of times in succession. I was therefore led to try another 
method of producing nervous shock ; and this I found a more effectual method than the 
one just described. It consisted in violently shaking the Sarsia in a bottle half filled 
with sea-water. I was surprised to find how violent and prolonged such shaking might 
be without any part of the apparently friable organism, except perhaps the tentacles 
and polypite, being broken or torn. The subsequent effects of shock were remarkable. 
For some little time after their restoration to the bell-jar, the Sarsias had lost, not only 
their spontaneity, but also their irritability ; for they would not respond even to the 
strongest stimulation. In the course of a few minutes, however, peripheral or muscular 
irritability returned, as shown by responses to nipping of the nervo-muscular sheet. 
The animals were now in the same condition as when anresthesiated by caffein or other 
central nerve poison ; but in a few minutes later central or reflex irritability also 
returned, as shown by single responses to single nippings of the tentacles. Last of all 
spontaneity began to return, and was in some few cases conspicuously marked by a 
want of coordination — all parts of the margin originating impulses at different times 
with the result of producing a continuous flurried, or shivering, movement of the necto- 
calyx. After a time, however, these movements became coordinated ; but in most cases 
when a swimming-bout had ended and a pause intervened, the next swimming-bout 
was always inaugurated by a period of shivering before coordination became established. 
This effect might last for a long time ; but eventually it, too, disappeared — the swimming- 
bouts then beginning with coordinated action in the usual way. 
