CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 7 
they constitute a serious menace to the cod fisheries by devouring the 
pelagic eggs and young fish. 
The elucidation of the minute anatomy of ctenophores has been one 
of the greatest triumphs of modern histology, and one with which one 
associates the names of Fol, Chun, R. Hertwig, Samassa, Grabe, and 
Bethe. 
Samassa was unable to demonstrate the existence of a nervous sys- 
tem in Ctenophores, but Bethe, 1895 (Biol. Centralblatt, Bd. 15, p. 140), 
placed living Cydippe in a solution of 1 in 4,000 of methylen blue in sea- 
water, and upon sectioning the Cydippe he claims to have found a sub- 
epithelial network of nervous nature. This consists of large, ganglionic 
cells scattered at fairly regular intervals. Each of these cells gives rise 
to 3 or 4 protoplasmic processes which fuse with like processes from other 
ganglia, thus appearing to form a nervous network without separate 
neurons; a condition so extraordinary that confirmatory studies must 
be made before we can accept it as proven. 
The experiments of Parker upon Mnemiopsis lend support to the 
conclusion that nervous elements may extend outward from the apical 
sense-organ along under the combs of cilia, or at any rate the normal 
rhythm of the ciliary combs is controlled by the nervous or muscular 
elements. I now find that in ctenophores when the muscles contract 
the cilia cease to beat, being inhibited by the stretching of the ciliated 
epithelium. A solution of 0.4 molecular MgCl, which inhibits mus- 
cular movement and produces relaxation, causes an incessant and very 
active movement of the cilia, but codrdinated movements of the rows 
of combs are usually destroyed, each comb beating independently of 
its neighbors and at an exceedingly rapid rate, uncontrolled by the 
nervous system. In M. mccradyi, however, coérdination is retained. 
From the physiological side there is evidence, but no proof, to sup- 
port the view that there is in ctenophores a nervous system compara- 
ble to that seen in higher metazoa. The results of such physiological 
researches are stated in this paper under Nmemiopsis and Beroé. 
Recently Bauer, 1910, Zeitschrift fiir Allgemeine Physiol., Jena, Bd. 10, 
p. 231; concludes that the combs of ctenophores are under the control 
of anervous system. He states that the nervous system can produce an 
acceleration or a retardation of the movements of the combs. Weak 
mechanical stimuli such as touching the mouth-region cause a stopping 
of the combs, while strong stimuli cause an acceleration. The sensory 
pole is without significance for this reflex. A summation of weak 
stimuli produces finally the effect of a single strong stimulus, and thus 
ctenophores show the well-known ‘‘treppe”’ effect which has been 
observed in higher forms. 
