Retrospective Criticism, 487 



Art. II. Retrospective Criticism, 



Corrections to the last Number. — For " Planaria corniita Johnston^* 

 p. 344— 346. read " Planaria vittata Montagu;''' and see p. 429. of the 

 present Number for the reasons. — J. D. 



• Luminosity of the Ocean. — I am happy to perceive that the attempt 

 which I made (Vol. IV. p. 505.), to reconcile the conflicting opinions of 

 naturalists upon this remarkable phenomenon, has called forth the addi- 

 tional interesting remarlcs of that indefatigable observer of nature, Mr. Bow- 

 man (Vol.V. p. l.)> from which it is evident that he is disposed to coincide in 

 my opinions, which are simply as follows: — 1st, That the light in general 

 originates in some matter or other (the exact nature of which is to be 

 ascertained only by chemical analysis), with which the surface of the ocean 

 may be impregnated, so as to produce the effect of emitting its luminosity 

 when disturbed; and, 2dly, that Mollusca, Medust^, Crustacea, &c., 

 may either, by mere contact with, or by feeding upon, or imbibing, such 

 matter, obtain the property of emitting, at second hand, this luminosity. 



The only minor point on which Mr. Bowman and myself differ is, that 

 I had imagined that it is only upon the contact of this matter with the 

 atmosphere that light is given out ; whilst Mr. Bowman (p. 2.) thinks that 

 this cannot be the case, " since it must always be in contact, from its 

 lying on the surface j yet," adds he, " we have abundant proof that it is 

 only excited by disturbance." I fancy, however, that we may respectively 

 say, that " each is right, and each is wrong ;" since, although it is evident, 

 as he suggests, that, in all cases, the light is excited by disturbance or 

 motion ; it appears equally evident, as I imagined, (at least, when the 

 presence of animals is not observed,) that it is only the portion of the 

 water which comes in contact with the atmosphere that throws out light, 

 and that the water beneath the surface does not exhibit this property. 



Upon the subject of the luminosity emitted by various animals in a 

 greater or less state of decomposition, the student may consult a paper in 

 the Philosophical Transactions for the year 1800, p. 161., pointed out to 

 me by my friend Sharpe, whose observations I noticed in my former com- 

 munication upon this subject. This gentleman tells us that the sailors say 

 that the light is caused by the sheathing of the hulk striking fire (steel 

 and flint fashion) with the water, in consequence of the rapid motion of 

 the vessel ! — J. O. Westwood. Jan. 21. 1832. 



A iew remarks on this interesting subject are presented by Mr. Wood- 

 ward, in the last Number, p. 302-3. — .7. D. 



On the Carrion Crow covering her Eggs with the Materials of the Lining of 

 the Nest. — " The carrion crow (Corvus Corone), for example, who lines 

 her nest with wool and rabbits' fur, always covers her eggs with a quan- 

 tity of this before leaving the nest." (See Rennie's plan of study in the 

 second edition of Montagu's Ornithological Dictionary.) In p. 144., 1 flatly 

 contradicted this extraordinary statement, on the strength of ray having 

 personally visited the nests of divers carrion crows, on the tops of trees 

 (" dreadful trade ! "), for the better part of forty years. The professor still 

 maintains (p. 393.) that " crows in the vicinity of Lee uniformly cover 

 their eggs, after they have begun to hatch, with the materials of the lining 

 of the nest ; " and he infers that the crows in the park at Walton Hall are 

 " eccentric crows " for not doing the same thing. ( See p. 393.) There 

 are just now seven carrion crows' nests in the trees in my park ; and 

 though I watch them with uncommon attention, and every now an'd then 

 mount up to them, I can find no traces whatever of their covering the eggs 

 with the lining of the nest. Now, will the professor have the goodness to 

 state to us, in the next Number of this Magazine, that he himself has 

 watched the carrion crows, in the vicinity of Lee, for hours and days 

 together, while hatching their eggs j and then, when the birds have left 



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