32 
MARINE FAUNA OF ST. ANDREWS. 
others, by the late Dr. John Reid, who obtained his examples 
at St. Andrews. 
On the whole we lack at St. Andrews the splendid profusion 
of the swimming jellies occasionally met with on our western 
shores, and especially in the Outer Hebrides, to which a 
favouring wind and tide sweep them from the warmer area of 
the Gulf-stream beyond, in company with lanthina and the 
Pteropods. Amongst these the strange and beautifully tinted 
Diphyes is seen darting hither and thither amongst the brilliant 
blues of its brethren with its trailing fringes of bright orange 
polypites; and on the lonely western shores, as at Monach, 
countless myriads of the little Velella are tossed in autumn on 
the sand. 
Mr. Darwin *, referring to the colours of certain Invertebrate 
animals, thinks that it is doubtful if such serve as a protection; 
but he goes on to observe that the perfect transparency of the 
Medusae, “ many floating mollusca, Crustacea, and even small 
oceanic fishes partake of this same glass-like structure,” and 
that u we can hardly doubt that they thus escape the notice 
of pelagic birds and other enemies.” It seems to me somewhat 
* Descent of Man, &c. vol. i. p. 323. 
