“THINGS UNRECK’D OF.” 165 
sand with only the siphonal orifices exposed to 
the light, perceives the shghtest shadow falling 
upon the water. This has led to closer study 
of the siphonal margins where what seem tiny 
eye specks have been detected. 
“We are told that some of our shellfishes 
are supplied with auditorial nerves, while an 
external ear is credited to some. Yet their 
whole external surface is so extremely sensitive, 
aside from the especially sensitive tentacula, 
that they perceive the approach of any object 
by vibration; hence naturalists tell us we need 
not expect a very strongly developed sense of 
sound. 
“Your last question I can best answer by 
reading you what some wise students have 
written concerning these interesting little crea- 
tures. ‘If you ask what can be the use of ears 
to a class of animals which are invariably dumb, 
I answer though this is true with respect to 
the great majority, yet it may be only that our 
senses are too dull to perceive the delicate 
sounds which they utter, and which may be 
sufficiently audible to their more sensitive or- | 
gans; and, besides, some mollusca can certainly 
emit sounds audible to us. Two very elegant 
species of sea-slug—viz., /olis punctata and 
Tritonia arborescens (now called Dendronotus 
