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Proceedings of the Pioyal Society 
answer to a query as to the possibility of floating molluscs containing 
colouring matters of the nature of chlorophyll, and after dying falling 
to the bottom of the ocean : — 
“ The green colouring matter from the ‘ Dacia,’ 533 fathoms, 
must have come, I think, from the corals and other organisms lying 
on the bottom, and not from the floating molluscs or other surface 
organisms.” 
The occurrence of chlorophyll in the depths of the ocean does not 
necessarily imply the presence of plant life, since spongilla have 
been found coloured by this substance (Hay Lankester, Quarterly 
Journal of Microscopical Science , 1882, p. 253), but it opens up the 
question whether rays of light are at all necessary for its production. 
The penetration of light to the bottom of the deep sea is a possible 
if not a probable phenomenon. It it true that in the clear w r aters 
of Lake Leman photographic dry-plates are affected at mid-day at 
no depth beyond 120 fathoms; but Messrs Fol and Sarasin are led 
to suppose that the greater transparency of sea- water will admit of 
the extreme limit of luminous rays reaching a still lower level. 
(“ Sur la Penetration de la Lumiere du Jour dans les Eaux duLac de 
Geneve,” Comptes Rendus , xcix. p. 783.) 
Facts at present at our disposal do not warrant the assumption 
that light cannot pass beyond this depth, for though the violet and 
ultra-violet certainly do not, as proved by Messrs Fol & Sarasin, yet 
water may transmit the green rays under circumstances which enable 
it to obscure the rest of the spectrum — the less refrangible portion by 
absorption, the more refrangible partly by absorption and partly by 
scattering. (See M. J. L Soret’s ‘‘Memoir Sur la Couleur de l’Eau,’’ 
Journal de Physique , 2nd series, vol. iii. 1884.) 
The reason why we have very little evidence at present of the 
penetration of great depths by green rays is owing to the fact that 
gelatine emulsion containing silver bromide is very slightly sensitive 
to such light. If any rays are necessary for the production of 
chlorophyll in plant life, which is extremely doubtful, they are those 
in the yellow and green lying between the solar lines D and E, this 
portion of the spectrum being transmitted bj the substance. We 
have accordingly no grounds for the conclusion that because chloro- 
phyll has been found at a depth of 553 fathoms, even if the pigment 
be produced in situ , therefore light has not penetrated so far, and 
has not operated in its formation. 
