1892.] Physiology. 1055 
The nervous system of the earwig, then, consists of, first, a series of 
centers which are capable, unaided, of responding to sensory stimulation 
by appropriate coordinated motions, in other words, a series of complex 
reflex centers lying in the ventral cord; and second, of a single 
ganglion situated in the head to which all the reflex centers are sub- 
ordinated, and which contains also the centers for the eye and the 
antennæ, and the seat of whatever intelligence may be present. 
Steiner (Die Funktionen des Centralnervensystems und ihre Phylo- 
genese ; Zweite Abtheilung: Die Fische) regards a true brain as defined 
by the presence of a general motor center together with the centers of 
at least one of the higher senses. The supermsophageal ganglion 
according to this definition is a brain, and indeed Steiner so regards it. 
The ventral cord is analogous in function to the spinal cord of 
some of the lower vertebrates, being a series of coordinated reflex 
centers, with perhaps some automatic functions also, all of which are 
subordinated to the brain. 
Some experiments of a similar nature were performed upon the 
Decapoda, but were not continued far enough to give any definite 
results except that, as would be expected, the superesophageal 
ganglion is a brain, and that of the ventral portion of the nervous 
system the thoracic ganglion is the highest and most complex in 
function. ; 
A few experiments upon the horse shoe crab (Limulus polyphemus) 
revealed the fact that the presence of the chain of small ganglia 
running backward, or even of part of it, even when entirely separated 
from the rest of the nervous system was sufficient to cause regular 
normal motion of the gills, which continued in some cases for two 
days, if the animals were left undisturbed in water. The motion 
usually ceases when the gills are exposed to the air or when they are 
suddenly stimulated but in a few moments the motion begins again if 
they are again covered with water. 
The results here given are not all new, but it is hoped that the 
statement concerning the more simple functions of the nervous system 
of the Lithobius may serve as a basis for further work, and for com- 
parison with the results obtained from other Invertebrates. 
C. M. Ca. 
Biological Laboratory, 
Wesleyan University, 
Middletown, Ct. 
74 
