270 JOURNAL OF COMPARATIVE NEUROLOGY. 
TABLE IV. 
Summary of experiments on Avenicola sp. 
Antero-posterior rate. 
No. of No. of records Length of : 
: Rance : Rate in cm. 
experiment Distal Proximal cord in cm. 
I 26 14 9 128.7 
2 41 30 15 106.5 
3 12 7 10 126.0 
Mean rate: 120.6 cm. per sec. 
Standard deviation: 9. 
Coefficient of variability: .07. 
Bispira polymorpha. 
This large tube inhabiting worm is very abundant near the 
lower limits of the tides. Their tubes are so well hidden in the 
crevices of the rocks and so firmly attached to them, that it is 
only with difficulty and great care that they can be removed 
without injury to the occupants. When undisturbed the head 
Fig. 5. Bispira polymorpha. Postero-anterior. Length of nerve cord be- 
tween distal and proximal electrodes: 28 cm. Rate: 700 cm. per sec. 
Time: 100 d.v. per sec. 
of the worm with the mass of constantly moving tentacles is pro- 
truded from the tube. On being disturbed it suddenly retracts 
its head and tentacles into the tube. Conformably with its 
mode of life, the musculature of the anterior portion of the 
body is greatly developed, especially that of the longitudinal 
