JENKINS AND Car son, Nervous Impulse in Worms. 273 
complicated dorsal structures of this worm together with the 
powerful contractions on irritation contribute to render the 
making of nerve-cord-muscle preparations difficult. The red 
pigmented nerve cord is nearly free in the body cavity and 
when the body is contracted the cord is thrown into loops, 
which necessitated the taking the cord out and straightening it 
before measuring the length involved. The musculature of the 
posterior end was taken as the reacting portion, and the antero- 
posterior rate only was determined. Although single induction 
shocks were not efficient at the distal points of stimulation to 
produce contractions in the longitudinal muscles of the reacting 
portion, they were found to be sufficient to set up a progressive 
movement of the setz from the point of stimulation posteriorly, 
indicating that their neuro-muscular apparatus is more irritable. 
This seemed to be further indicated by the fact that the animal 
could be quite roughly handled without producing contractions 
of the longitudinal muscles, while the sete reacted to the 
treatment. 
F.XPERIMENT No. 2, Table VI, antero-posterior, temp. 15°C, Jan. 19, 1902. 
‘Distal Proximal 
No. of records 25 18 
Mean latent time 0.422 sec 0.26 sec. 
Standard deviation 0.045 sec. 0.03 sec. 
Coefficient of variability _ +10 SDE 
Length of cord: 9 cm. (17 segments). . Rate; tees 25 cm. per sec. 
ABER Vile 
Summary of Experiments on Aphrodite sp. 
Antero-posterior rate. 
“No of. | po lawee a vecords. ; | Length ae e 
experiment | Distal | Promina | cord in cm. ate In cm. 
I 34 3 } 52.8 
. Sade ee Ce, Nea ee ee 
Average r: rate: 54-5 cm, per sec. 
Polynoe pulchra. 
This worm lives on the surface of the oral tentacles of the 
large sea cucumber, folothuria californica, and in the mouth 
cavity of the large key-hole limpet, Lacopzna crenulata, both of 
which are common at Pacific Grove. This species of Polynoe 
reaches a length of from 4 to5 cm. On account of the delicacy 
of its structure the nerve-cord is exposed with some difficulty. 
The worm also breaks in pieces very readily, neither chloralhy- 
