Mr. R. M‘Andrew on Mr. Jeffreys’s last Dredging Report. 361 
am acquainted with. In the former case they were littoral, in 
the latter on a red Yucus obtained from a depth of from 10 to 
20 fathoms. 
4. “The colour of specimens from the greatest depths is not 
less vivid than from shallow water,” &c. This statement 
would imply either that no rays of light are intercepted or de- 
flected in their passage through water (in which case we ought 
to be able to see objects as well through this medium as through 
air)—or that light has no effect upon colour, which I may ven- 
ture to say is not the case. I have no reason to suppose that 
colour is affected by depth, except in relation to the supply of 
light, or that the effect of light is appreciable except where 
the colour is superficial. The colour of our blood may be 
independent of the action of light, though not so that of our 
complexions. It should be observed that in some of the ex- 
amples mentioned by Mr. Jeffreys the colouring-matter per- 
meates the substance of the shell; and with respect to Venus 
ovata | must add that my experience is at variance with his 
statement, which I therefore presume must be founded upon 
some exceptional case. There are in the ‘national collection 
specimens, not selected, of Venus ovata and JV. striatula, pro- 
cured by me from a depth of 80 fathoms and upwards, which 
will be found to be of a chalky consistency and almost desti- 
tute of colour. 
The effect of light in heightening the superficial colour, 
particularly the brighter hues of shells, is evident on comparing 
together specimens of the same species from different latitudes. 
Venus ovata, V. verrucosa, V. casina, all the British species of 
Tapes, Circe minima, and many others have much more colour 
in the latitude of the Mediterranean than in our seas, which 
is naturally attributable to exposure to a more intense light. 
It is a remark of Forbes, which my own observation has 
confirmed, that the species of Mollusca peculiar to great depths 
are generally void of colour. 
Of the remaining propositions I will only remark upon 
7. “Exotic and oceanic shells are carried northward by 
westerly winds, and not directly by the Gulf-stream, which 
does not reach our coasts,” that I do not see how the distribu- 
tion of Mollusca inhabiting the bottom of the sea can be 
affected by winds, from the direct influence of which they are 
so effectually removed. With respect to animals frequenting 
the surface of the ocean, such as anthina and Velella, which 
occasionally appear on our coasts in considerable numbers 
after a prevalence of westerly or south-westerly winds, they 
are temporary visitors, and have not succeeded in establishing 
themselves permanently in our seas. 
