FUNDAMENTAL EXPERIMENTS, 35 
eyed Meduse, I find it to be uniformly true that 
removal of the extreme periphery of the animal 
causes instantaneous, complete, and permanent 
paralysis of the locomotor system. In the genus 
Sarsia, my observations point very decidedly to 
the conclusion that the principal locomotor centres 
are the marginal bodies, but that, nevertheless, 
every microscopical portion of the intertentacular 
spaces of the margin is likewise endowed with 
the property of originating locomotor impulses. 
In the covered-eyed division of the Medusz, I find 
that the principal seat of spontaneity is the 
margin, but that the latter is not, as in the naked- 
eyed Medusz, the exclusive seat of spontaneity. 
Although in the vast majority of cases I have found 
that excision of the margin impairs or destroys the 
spontaneity of the animal for a time, I have also 
found that the paralysis so produced is very seldom 
of a permanent nature. After a variable period 
occasional contractions are usually given, or, in 
some cases, the contractions may be resumed with 
but little apparent detriment. Considerable differ- 
ences, however, in these respects are manifested by 
different species, and also by different individuals 
of the same species. Hence, in comparing the 
covered-eyed group as a whole with the naked-eyed 
group as a whole, so far as my observations extend, 
I should say that the former resembles the latter in 
that its representatives usually have their main 
supply of locomotor centres situated in their 
margins, but that it differs from the latter in that 
its representatives usually have a greater or less 
