TACTILE RESPONSES OF DE-EYED HAMLET 167 
cleaned; metal rods or wires were brightly polished and the 
strips of wood were freshly planed. Tests were made with rods 
immediately after cleaning and also when they had lain in sea- 
water for an hour or more. ‘The substances used were: 
Metals: copper, platinum, gold, zinc, cadmium, aluminum, 
wrought iron, steel, galvanized iron, and brass. 
Woods: ‘cedar,’ spruce, oak, elm and cypress. 
Miscellaneous: glass, hard rubber, sealing-wax, soft rubber 
(red, white, and black tubing), porcelain, hard paraffin, sand- 
stone, and compressed carbon. 
The great variety of materials which induced the same re- 
sponse is sufficient to show that the process of stimulation did 
not depend upon the diffusion of chemical excitants nor (in the © 
ease of the metals) upon any ‘action at a distance,’ either pri- 
marily electrical or through the escape of charged atoms of 
metal (cf. Mathews, 07). The cadmium stick and the wires of 
platinum used in the tests were particularly pure, and no dif- 
ference in the response they induced could be detected after they 
had been covered with neutral paraffin. The reactions are some- 
what variable, and it is conceivable that some substance may 
stimulate in this fashion (i.e., ‘chemically’) more than others, 
but I could find no evidence of it in the hamlet. This point 
was tested with some care, because I had learned from Prof. 
G. H. Parker of reactions found by him with the catfish when 
approached by metal rods. Nor could I find anything of this 
sort in Amphioxus, Balanoglossus, sea-anemones, crabs (blinded), 
the ‘rhinophores’ of nudibranchs, or several teleosts that were 
examined. 
Rods of brass, iron, glass, or wood of different diameters and 
shapes were then tried. Fishes of fairly uniform size (about 30 
em. length) were used in comparative experiments. ‘To avoid, 
as far as possible, communicating undesired trembling movements 
to the rods, and thus to the water, the rods were in many tests 
clamped firmly in the middle of the aquarium and the behavior 
of the blinded hamlet when approaching them during slow swim- 
ming movements was compared with the result when a rod was 
earefully brought near a part of the body. The result was in 
