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that in any given case the chances are in favour of the individual experimented upon 
having most or all of its spontaneity aggregated, so to speak, in its eight lithocysts. If 
seven of these, therefore, be removed, all the spontaneous impulses to contraction must 
emanate from the remaining lithocyst. Indeed it may easily be seen that such is the case ; 
for each pulsation of the gonocalyx is now of the nature of a double wave of contraction 
— the two waves starting simultaneously from the remaining lithocyst, each to run rapidly 
and equally in opposite directions, and so to meet at the point of the gonocalyx that 
is opposite to the lithocyst. Well, if this remaining lithocyst be made the point of 
origin of a spiral section which is carried round and round the flat-shaped disk, the 
result of course is a long strip of tissue, terminating at one end in the lithocyst, and at 
the other end in the remainder of the gonocalyx (see Plate 33*). A contractile 
wave proceeding from the lithocyst has now either to become blocked at some point in 
the length of the strip, or to traverse the whole length of the strip and deliver itself 
into the remaining contractile tissue of the gonocalyx. The conditions which deter- 
mine the blocking of a contractile wave under these circumstances will be fully treated 
of further on : meanwhile it is enough to say that, as might be expected, the length 
and width of the strip are very important factors, but that, nevertheless, there are 
immense individual differences in the endurance of the contractile tissue under this 
form of section. The highest degree of such endurance that I have met with has been 
two and a half turns of the spiral (see Plate 33). The strip in this case was about an 
inch wide and nearly a yard long. I doubt not, however, that a wonder-seeker, by making 
a sufficient number of such experiments, could obtain results even more surprising. 
( d ) The second observation will be best appreciated by a glance at the accompanying 
woodcut (fig. 3), which is a drawing made from life of an individual submitted to radial 
Eig. 3. 
section in the way represented. The contractions emanating from the remaining 
lithocyst ( l ) passed through the entire gonocalyx with no appreciable diminution of 
vigor, so that I would have increased the severity of the section but for want of space. 
* The central organs in this and in the preceding Plate are partly copied from Prof. L. Agassiz’s represen- 
tation of an allied species, and so are not perfectly accurate. 
