174. W. J. CROZIER 
Inasmuch as tactile sensitivity of a very highly developed 
character is present in the hamlet possessing well-developed func- 
tional eyes, there is no reason to believe that a similar superior 
degree of tactile irritability has been developed in the blind cave 
fishes as the result of their lack of vision.’ 
Concerning the function of this sense in Epinephelus, it may be 
suggested that it is useful at night or when the fish is maneuver- 
ing in darkened crannies of the ‘coral reefs.’ 
SUMMARY 
The de-eyed hamlet (Epinephelus striatus) gives well-defined 
reactions to the near approach of solid bodies. In the seeing 
fish this form of sensitivity is present, but motor effects which it 
might induce are almost completely inhibited. Mechanical de- 
formations in the water of very minute amplitude and of a some- 
what irregular nature are the source of stimulation in these re- 
sponses, which cannot be attributed to chemical or to electrical 
disturbances. The presence of this exceedingly delicate form of 
sensitivity, generally distributed over the surface of the fish and 
leading to deliberate reactions of a well-defined character, has 
been used to discover any influence of chemical excitants, locally 
applied, upon the end organs of tactile sensitivity. Although 
the existence of this ‘epicritic’ form of irritability interferes with 
any direct study of the mode of excitation in ‘common chemical 
sense’ reactions, it can nevertheless be shown, with its aid, that 
the generally distributed ‘common chemical’ irritability of this 
fish does not involve tactile receptors. Since the hamlet with 
well-developed eyes exhibits a high degree of tactile discrimina- 
tion, such as has been described for blind cave fishes,—although 
the existence of this sensitivity would be quite overlooked unless 
71It should be added that after living in the laboratory for more than four 
months after the removal of the eyes, three hamlets were carefully compared 
with several others recently de-eyed as regards their comparative ‘tactile’ 
irritability; no differences could be detected. Hence continued lack of vision 
does not lead to an increased development of the hamlet’s ‘epicritic’ tactile 
irritability. i 
