PARKER: THE REACTIONS OF METRIDIUM. ae 
be taken as a proof of the lack of physiological centralization in the ner- 
vous functions of these low organisms, a condition that corresponds with 
the diffuse state of their nervous systems. 
August 24, 1895, August 27, 1895. 
R. Side. L. Side. R. Side. 
il Meat 85 sec. 45 sec. 40 sec. 55 sec. 
2 Paper 80 “ SOs 60)“ TAU) 
5 Meat 5 es Ab as BO! * Son! 
4 Paper SD) hy (os) BE) et 45 “ 
5 Meat 49 * AB) s 30 “ 45) 
6 Paper 105 “ HDi 1 Ua 65 “ 
U Meat BOs 35 ome 40 « 
8 Paper fe) 105 “ GOA 55 “ 
9 Meat (i) oon AA & Sis) 
10 Paper @ 357 55“ Jone 
11 Meat 40 “ 30 “ 45 “ ay & 
12 Paper oa ohm 63“ 146: $ 
13 Meat Sone 30 “ 45 “ 
14 Paper fo foe fore 
30 
Summary. — The outer surfaces of the column and aboral disk of 
Metridium marginatum are not ciliated, and are incapable of being 
stimulated by the soluble constituents of the food. 
The tentacles are covered with cilia that wave always from the base 
of these organs towards their tips. The action of these cilia was not 
noticeably influenced by the soluble constituents of the food. 
The tentacles normally rest with their tips pointed away from the 
mouth. When stimulated with meat juice, they point temporarily 
toward the mouth (muscular response). Many other substances, sugar, 
quinine, etc., fail to stimulate them. 
The intermediate zone of the oral disk is probably devoid of cilia, or 
possesses at most only a few patches ; these, if present, wave away from 
the mouth. This region cannot be stimulated by the soluble parts of 
the food. 
