I4O MANTON COPELAND. 



nerves, but through the protoplasm of the ciliated cells, a kind of 

 transmission which on account of its resemblance to the nervous 

 type has been designated neuroid. In the course of investigations 

 on the behavior of cilia on the excised foot of the snail Alectrion 

 trivittata (Say) the wave-like spread of action was clearly observed 

 (Copeland, '19). Cilia quiescent over a limited area of the foot 

 suddenly became active, others close by then began beating, and as 

 the wave of action continued many were in motion. After a time 

 they came to rest again. To account for this behavior, and the 

 fact that cilia start beating over the entire ventral surface of the 

 foot when the snail begins locomotion, one might assume that rest- 

 ing cilia are excited to movement in some definite region of the 

 foot through impulses received from the nervous system, and that 

 neuroid, or intraepithelial transmission, spreading from this center, 

 brings about the activity of the remaining cilia. This possibility 

 is rendered improbable, however, from the fact that if two ob- 

 servers are watching carefully the sand-covered surface of the foot 

 of Polinices when the snail begins the righting reaction, no differ- 

 ence can be detected in the time when the sand grains begin move- 

 ment, although the two points under observation may be ten centi- 

 meters apart. 



In order to gain more definite information on the method of 

 transmission in Polinices the following experiments were tried. 

 After anesthetizing a snail in magnesium sulphate, the epithelium 

 near the center of the foot was cut in such a way that an area 

 25 mm. long and 18 mm. wide was isolated from the surrounding 

 epithelium. When the animal became active again after the opera- 

 tion the cilia on the isolated epithelium behaved the same as those 

 over other parts of the foot, as far as could be determined by 

 testing with sand grains. As long as the snail rested upside down 

 there was no movement of the mucus or sand on the foot, but when 

 it attempted to right itself ciliary activity began on the isolated 

 patch of epithelium, as well as elsewhere, and continued until the 

 animal rested again. Following this test more of the epithelium 

 was cut away so that the subepithelial tissues were exposed in a 

 well-defined band completely surrounding the epithelial island. 

 The ciliary behavior was the same as before. The test was re- 

 peated on Polinices hcros, an area of epithelium 13 to 15 mm. in 



