PRIMARY INHIBITION OF CILIARY MOVEMENT 435 
R. S. Lillie (08, pp. 200, 219) has described certain phenomena 
of primary inhibition in Eucharis and Mnemiopsis that do not 
appear when Ca salts are not present: ‘Slight stimulation of a 
row of beating plates, a detached portion of a row, or even an 
active individual plate, with the extremity of a glass rod, is typi- 
cally followed by immediate and complete cessation of movement. 
After an interval activity is resumed.” ‘‘This susceptibility to 
mechanical inhibition is dependent on the presence of calcium 
salts.” My material of Beroé was not sufficiently abundant to 
test whether the inhibitory mechanism in Beroé described above 
also needs the presence of calcium salts if it is to function. In 
three specimens of Pleurobrachia which on different occasions 
during the summer of 1913 I investigated in artificial sea-water 
according to Forchhammer’s (cf. Knudsen, p. 16) prescription, 
but with a total exclusion of Ca, spontaneous ciliary activity of a 
fairly normal character went on for about two hours. It may be 
mentioned in passing that the most striking effect of the absence 
of Ca on this animal was a paralysis of the tentacles, which ceased 
when the animal was put back again into complete sea-water. 
From the observations cited it is only shown, with regard to the 
main question, that if the ciliary apparatus in Beroé resists the 
absence of Ca salts as long as in Pleurobrachia, one ought easily 
to be able to carry out, by using an electric current, a test as 
to whether the inhibitory apparatus in Beroé depends for is 
function on the presence of Ca salts. 
The proofs given in this work of a primarily cilio-inhibitory 
mechanism in Beroé which follows in several respects the physi- 
ological and pharmacodynamic laws for a nervous formation 
are, as is seen from the preceding, based exclusively on tests as 
to function. It is no part of the plan of my work to investigate 
whether the substratum of this inhibitory mechanism is composed 
of elements which also deserve the name of nerve elements. 
This question, however, has such a great general importance that 
I cannot neglect it altogether in this connection, even if I cannot 
contribute toward its solution anything more than what is to 
be obtained from the literature. — ; 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 31, No. 4 
