236 TRANSMISSION OF NERVE NET OF CCELENTERATES 



In Specimen A the average reaction time over the tongue of tissue 

 was found to be 1.493 seconds and from the root of the tongue 0.613 

 seconds, which agrees very closely with that of the intact animal, 

 0.60 seconds. The time consumed in transmission over the tongue is 

 the difference between 1.493 and 0.613 or 0.880 seconds. As the 

 length of the tongue between the points stimulated was 119 mm., 

 it follows that the rate of transmission was a little over 135 mm. per 

 second. By a similar method of procedure the rate in Specimen B 

 was determined to be 121 mm. per second, and in Specimen C 146 

 mm. per second. 



These rates are relatively low compared with even the lower rates 

 already determined for transmission in the nerve fibers of metazoans, 

 but this is not surprising, for the nerve net has generally been sup- 

 posed to be a less rapid and efficient organ of transmission than the 

 nerve trunk. The rate is lower than that given by Romanes (1878) 

 for what he calls the stimulus wave in Aurelia, namely 9 inches or 

 about 229 mm. per second, and is much lower than that given by 

 Harvey (1912) for the contraction wave in Cassiopea, some 775 mm. 

 per second. In both these instances, however, the rates measured 

 refer to waves of muscular activity and though these waves very 

 probably reflect accurately the rate of nervous transmission, they are 

 not free from complications with possible muscular transmission, 

 whereas the rates derived from Metridium are. The measurements 

 taken on Cassiopea were made at Dry Tortugas, Florida, where 

 the sea water is relatively warm, a condition which, as is well known, 

 increases the rate of transmission. At V/oods Hole, Massachusetts, 

 where the measurements on Metridium were made, the sea water in 

 which the sea anemones were immersed during experimentation had a 

 temperature of 21°C. 



CONCLUSION. 



Nerve net transmission in Metridium at 21°C. varies from 121 to 



146 mm. per second. 



BIBLIOGRAPHY. 



Harvey, E. N., 1912, The permeability of living cells for alkalies. The question 

 of nerve fatigue, Carnegie Institution of Washington, Year Book, No. 10, 130- 

 131. 



Romanes, G. J., 1878, Further observations on the locomotor system of medusae, 

 Phit. Tr. Roy. Soc, clxvii, 659-752. 



