ME. G-. J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDUSAE. 
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marked. The three individuals which still had their eye-specks sought the light as 
before, while the nine without their eye-specks swam hither and thither without paying 
it any regard. 
A further question, however, still remained to be determined. The pigment-spot 
of the eye-speck in Medusse is, as Agassiz observes, placed in front of the presumably 
nervous tissue ; and for this reason he naturally enough suggests that if the eye-speck 
has a visual function to perform, the probability is that the rays by which the organ is 
affected are the heat-rays lying beyond the range of the visible spectrum. Accordingly 
I brought a heated iron just ceasing to be red close against the large bell-jar which 
contained the numerous specimens of Sarsia ; but not one of the latter approached the 
heated metal. 
From these observations, therefore, I conclude that in Sarsia the faculty of appre- 
ciating luminous rays is present, and that this faculty is lodged exclusively in the eye- 
specks. My observations on the other genera of Meduste in this connexion are not 
yet complete. 
§ 2. Effects of various Poisons on the Locomotor System of Medusas. — -As this com- 
munication has now grown to an undue length, I shall reserve for a future paper many 
facts of great physiological interest regarding luminosity, general distribution of the 
supposed lines of discharge, coordination of the centres of spontaneity, rate of transmission 
of contractile waves in different genera and under various forms of section, &c., and shall 
conclude what I have to say at the present time by describing the effects of a few among 
the poisons I have tried upon the Medusae, choosing those upon the list which most 
tend to prove the identity of the specialized marginal tissue of these animals with 
nervous tissue in general. 
(a) The anaesthesiating influence of chloroform and ether is most decided. This 
fact, I find, has also been observed by Agassiz ; and he remarks in effect that even if it 
stood alone it ought to be considered sufficient to demonstrate the presence of nerves 
in Medusae. Without straining our deductive powers quite so far as this, I think that 
the marked influence of chloroform and ether upon the Medusae may properly be taken 
as in some measure confirmatory of the doctrine which that great naturalist so strenu- 
ously upheld. 
Agassiz appears to have tried the effect of chloroform only in the case of Sarsia. I 
may therefore state that in all the other genera I have experimented upon, both of the 
naked- and covered-eyed groups, the anaesthesiating influence of this substance is equally 
decided. This influence, moreover, is in every respect precisely similar to that which 
is observable in the case of the higher animals. Soon after a few drops of chloroform 
have been added to the water in which a vigorous medusid is contained, the locomotor 
pulsations of the latter become slower and slower in the time occupied by their execu- 
tion, while the intervals of diastole become more and more prolonged. Concurrently 
with this slowing of the pulsations their strength naturally grows less and less vigorous, 
so that eventually the systoles are separated from one another by five or six times the 
