MR. Gr. J. EOMAfflS ON THE LOCOMOTOR SYSTEM OE MERITS #1. 
29 ; 
to regard the hypothetical plexus as presenting the high degree of integration charac- 
teristic of a properly nervous plexus ; but in this preliminary paper I cannot, without 
undue length, discuss this subject. 
( c ) The strongest evidence of definite lines of discharge being present, however, is 
yet to be adduced ; and this consists in the following invariable fact : — At whatever point 
in a strip that is being progressively elongated by section the contractile wave becomes 
blocked , the blocking is sure to take place completely and exclusively at that point. Whereas 
up to the time that the incision reached quite up to that point the contractile waves 
showed no signs of meeting with any resistance in their passage from the severed strip 
to the rest of the gonocalyx, immediately after the incision is carried through that point 
the blocking of the contractile waves is total. Now, as I have tried this experiment a 
great number of times, and always tried it by carefully feeling the way round ( i . e. only 
making a very short continuation of the cut after the occurrence of each contractile 
wave, and so very precisely localizing the spot at which the contractile waves ceased to 
pass into the gonocalyx), I can scarcely doubt that in every case the blocking is caused 
by cutting through a very slender line of tissue which was in some way or other differ- 
entiated from the surrounding tissue, and which, in virtue of its differentiation, had 
previously served to convey the contractile influence from the strip to the remainder of 
the gonocalyx. Why it should sometimes be so long before such slender lines of tissue 
are encountered by the section, or a sufficient number of them encountered to destroy 
the physiological continuity of the tissue, may well afford matter for surprise ; but I 
must nevertheless assert my persuasion that, so far as my observations have yet gone, a 
legitimate deduction from them appears to be, that in every individual of this species (and 
so from analogy, as well as observations on other species, probably in all the Medusae) 
these slender lines of differentiated tissue are present, that through their mediation the 
spontaneous impulses originating in the marginal centres are communicated to the con- 
tractile tissue of the swimming-organ, and therefore that these slender lines of differ- 
entiated tissue are functionally, if not structurally, nerves. 
Although 1 intend for the present to reserve my observations on the histological 
part of the inquiry, I may here state, in passing, that I have hitherto failed to distin- 
guish any structural modification of the tissue in the regions occupied by these supposed 
lines of discharge. On one occasion, when I made the radial incision on one side 
of the single remaining lithocyst, preparatory to making the circumferential incision 
necessary to procure a contractile strip, I was surprised to find that the entire gono- 
calyx, although previously contracting with vigour, became wholly paralyzed. Now the 
incision which I made was only half an inch long, and the effect it produced was amply 
sufficient to prove that the influence of the lithocyst had previously been communicated 
to the gonocalyx from one side only. I therefore concluded that somewhere within the 
small band of tissue half an inch long and quarter of an inch broad, which was included 
between the incision and the lithocyst, there must have been a line of discharge of 
sufficient size to convey the influence of the lithocyst to the entire gonocalyx. Yet 
MDCCCLXXVI. 2 T 
