430 GUSTAF FR. GOTHLIN 
‘“When a Mnemiopsis is shaken in sea-water it can be broken 
easily into fragments and the plates attached to these pieces will 
continue to beat rhythmically and metachronally for from one 
to two days. . . . in Mnemiopsis even a single plate with 
a small basal piece of protoplasm will beat rhythmically for a long 
time.’ ~ It will probably be obvious that a low degree of autom- 
atism must be a favorable factor for inhibitory influences, since 
by means of it the latter have a smaller resistance to overcome. 
It seems to me, therefore, to be probable that there is a certain 
connection between the marked lability to inhibition shown by 
the meridional rows in Beroé and the slight automatism of its 
separate swimming plates. I have not investigated systemati- 
cally whether such ctenophores as, like Bolina, have swimming 
plates with more developed automatism also have a primary 
inhibitory apparatus. As I have shown in an earlier work, the 
transmission of a longitudinal oro-central current causes in Bo- 
lina and Pleurobrachia a marked increase in the frequency of 
the ciliary waves, which is obviously the contrary to what is the 
case in Beroé. In Bolina, however, this increase is preceded by 
a short stoppage, limited to a fraction of a second (’17, exp. II 
and III). Whether this stoppage presupposes a mechanism for 
primary inhibition or whether there is such a mechanism at all 
in any other ctenophore except Beroé, I consider, however, to 
be a still unsolved problem. 
A number of observations support the idea that the sirannerece 
in the separate plates in Beroé is not equally marked in all parts 
of a row, but is more marked in its aboral part, less in its oral 
part. Thus Th. Eimer (’73, p. 45, note 3) cites the following 
observation made in the case of expiring animals: ‘‘ Die in der 
Gegend des Mundes gelegenen Plittchen sind lingst todt, wah- 
rend die iibrigen noch lustig fortschwingen.”’ In my experiment 
3 it is seen that when an oro-central current of density 2.47 
m.amp./em.? has been transmitted for a short while through an 
animal slightly poisoned with chloral hydrate and during this 
time has maintained total inhibition, after the current is broken 
the first waves are limited to a short piece of the row nearest to 
the sensory pole, while the subsequent ones extend farther and 
