A VISIT TO MADEIRA AND THE CANARY ISLANDS. 129 
In the deeper pools, at low water, Holothurians were 
common, as also Aplysia (sea-hare) of very large size, 
some measuring nearly one foot in length. Some were of 
a dark purple, others a light grey marked with black. 
When disturbed they emitted a deep purplish fluid staining 
everything around. One of our nets was indelibly dyed 
by it. Darwin, in ‘‘The Voyage of the Beagle,’’ describes 
this large species, and states that it has ‘‘an acrid secretion 
spread over the body, which causes a sharp, stinging 
sensation, similar to that produced by the Physalia, or 
Portuguese man-of-war.”’ Several which we handled freely 
certainly did not exhibit this power. 
About the rocks, above high water mark, we noticed 
quantities of moderately sized, flat, black crabs, very active 
in movement, and in the pools an extremely fragile white 
crab, beautifully marked with red, and which broke almost 
with a touch. At high water mark all along the beach we 
found quantities of pumice stone. 
The sunsets here were wonderfully gorgeous, and the 
varied hues of light over the Peak singularly beautiful ; 
while in the distance, sixty miles off, was clearly visible 
the dark outlines of the Island of Palma. The twilight 
is very short, and at midsummer it is dark about six p.m., 
when the frogs at once commence their innings and keep 
it up vigorously. On one occasion we tow-netted after 
dark, about a mile out, and brought up a quantity of phos- 
phorescent schizopods, some of which Mr. A. O. Walker, 
F.L.S., has kindly undertaken to examine and report upon. 
