PARKER: THE REACTIONS OF METRIDIUM. 31% 
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. Sido. R. Side. L. Side. 
1 Meat 85 sec. 45 sec. 40 sec. 55 sec 
2 Paper 80.“ 90 “ iU s 0 
8 Meat 50 “ 45 * 50 “ 85 * 
4 Paper QU 00 55 * 45 „ 
5 Meat 40 “ 45 “ eoo 45 “ 
6 Paper 105 “ 585 * T0 65 * 
y Meat 00 £ 8 85 * 40 * 
8 Paper oo US uno 55 “ 
9 Meat mss 35 “ 20 “ 86 “ 
10 Paper oo oo 55 “ 95 “ 
11 Meat 40 “ Boe 45 * aee 
12 Paper oo 95 „ 63 * 145 * 
13 Meat 35 “ uU us 45 * 
14 Paper 00 oo 00 
15 Meat uh €" 40 “ 30 * 
16 Paper 00 65 * wur 
17 Meat 35 “ 45 * 
18 Paper 00 oo 
19 Meat 35 * Bu“ 
20 Paper 00 00 
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, ete., 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. 
