30 



NATURE 



[November 12, 1891 



time Iroin one to three inclus thick, and the water is, of course, 

 a saturated brine. It is interesting to note, however, that it 

 does not correspond in composition with the water from the 

 ocean. Like the Dead Sea, the lake contains an excessive 

 quantity of calcium salt. 



The interior of the crater basin is crusted in many places with 

 deposits of carbonate of calcium, proving that it was at one time 

 occupied by a highly calcareous water, probably of high tem- 

 perature. I have given in connection with the results of my 

 analysis, which extends only to the constituents present in large 

 amount, an analysis of concentrated sea-water from the salt 

 works of Kakaako, and an average of a number of analyses that 

 have been made of the waters of the Dead Sea. These latter 

 sometimes contain a larger proportion of solids than the average 

 figure, but in no analy.'^is that I have seen has the quantity been 

 as large as that found in the water of Aalia Paakal. 



Honolulu, October i6. 



A. B. Lyons. 



Meretrix, Lamarck, 1799, versus Cytherea, Lamarck, 1806. 



In the notice of Mr. Newton's "List of Mollusca," in 

 Nature of October 29 (vol, xliv. p. 610), I read as follows : — 

 "Many old favourites have been thus relegated to obscurity, 

 whilst fresh names, dug up from some forgotten corner, have, 

 by the law of priority, taken their places. Thus, Meretrix, 

 Lamarck, 1799, takes the place of his better-known Cytherea of 

 1806, the latter having been applied by Fabricius, in 1805, to a 

 dipterous insect." 



The Dipteron Cytherea obscura, Fab. 1805, was de- 

 scribed nine years later than Mutio obscnrus, Lalreille (1796), 

 which is the same species. Meigen, in his principal work 

 (1820), acknowledged the priority, and the insect has been 

 called Ahitio ever since. As the typical species is the same for 

 both genera, there is no chance whatever for Cytherea to be 

 resuscitated, and it may well remain as the name of the Mollusk. 

 I most heartily agree with the opinion of the reviewer, that "it 

 would be an immense gain if every name proposed to be altered 

 had to pass through a regularly-constituted committee of inves- 

 tigation before it was accepted and allowed to pass current." In 

 such a committee, besides /r/(?;7V^, two other paramount scien- 

 tific interests should be consulted, and they are — contimiity and 

 authority. C. R. OSTEN Sacken. 



Heidelberg, November i. 



A Plague of Frogs, 



I HAVE just read with great interest the letter in Nature of 

 the 5th inst. (p. 8), signed R. Haig Thomas, apropos of frogs 

 entering his cellar. 



During the past seven years I have resided in three separate 

 lodgings (no two being within half a mile of the other), each 

 having a small garden at the back surrounded by a solid wall. 

 The lowest of these was about 5 feet, and in two cases the 

 walls were quite bare. In the third case there were creepers 

 on both sides. But in all three cases has 07ie frog suddenly 

 made its appearance, and always during very wet weather. To 

 account for their entrance has completely puzzled me. 



B. A. MUIRHEAD. 



Pall Mall Club, Waterloo Place, November 8. 



NO. II 50, VOL. 45] 



Red Light after Sunset, 



There was at Lyon.=, N.Y., last evening, a magnificent dis- 

 play of red light similar to the sunset glows which attracted so 

 much attention a few years ago. The entiie western sky was of 

 a deep lurid red, resembling a conflagration, for three-quarters, 

 of an hour or more after sunset, M. A. Veeder. 



Lyons, N.Y., October 30. 



Topical Selection and Mimicry. 

 Will you permit me to make a few remarks on Dr. A. R. 

 Wallace's review of my book ("On the Modification of Organ- 

 isms ") which appeared in your journal on April 9 last (vol. xHii. 

 p. 529)? I cannot disguise from myself the fact that in attempting 

 any reply I labour under great disadvantages : first, in having to 

 combat the statements of such a high authority as Dr. Wallace ; 

 and secondly, in writing as I am from the Antipodes, my reply 

 cannot reach your readers for at least three months after the 

 publication of the review in question. Nevertheless there are 

 two statements made by him which demand some notice from mc. 

 The first is that I have misrepresented Darwin's views on the 

 question of natural selection. My reply to this is distinct and 

 emphatic. The references to Darwin in my book are absolutely 

 correct : there is no misrepresentation ; there is no misquotation. 

 In every reference to Darwin's views I gave the page and the 

 edition from which the quotation was taken. In writing my 

 book I was perfectly aware how important it was to start with a 

 clear understanding of what Darwin meant by the term natural 

 selection, and I was at the utmost pains to quote his exact words 

 in every reference I made to him. It is not my fault if Darwin, 

 did not give a clear or consistent definition of natural selection, 

 or that he confounded cause with effect, as when at one time he 

 defined natural selection as " the struggle for existence," and at 

 another time as " the survival of the fittest." I can therefore 

 with the utmost confidence refer your readers to the book itself 

 in confirmation of what I here state. 



Dr.- Wallace has also been good enough to give, as a sample 

 of my "teaching," a part of a sentence of mine on the subject of 

 mimicry. He says your readers "may estimate the value of 

 Mr. Syme's teaching by his explanation of mimicry, which is, 

 that natural selection has nothing to do with it, but that insects 

 choose environments to match their own colours. He tells us 

 that these extraordinary resemblances only occur among insects 

 that are sluggish, and that ' to account for the likeness to special 

 objects, animate or inanimate, we have only to assume that these 

 defenceless creatures have intelligence enough to perceive that 

 their safety lies in escaping observation.' " 



Now I did not state that these extraordinary resemblances 

 occurred only among insects ; what I said was that they occurred 

 "chiefly" among insects. I am aware that, judging from Dr. 

 Wallace's stand-point, I may have disposed of the subject of 

 mimicry in a somewhat off-hand way, and for the simple reason 

 that I regarded mimicry as a subordinate branch of the more 

 important subject of protective coloration, which I had treated at 

 some length ; and in adopting this course 1 was taking as my 

 guide Dr. Wallace himself, who has elsewhere stated that "the 

 resemblance of one animal to another is of exactly the same 

 essential nature as the resemblance to a leaf, or to bark, or to 

 desert ssand, and answers exactly the same purpose " ("Natural 

 Selection," p. 124, 2nd edition). So far, then, I may presume 

 that I am in good company. To understand what I said about 

 mimicry, therefore, it is necessary to know my views on protec- 

 tive coloration. Protective coloration I regarded as, in certain 

 cases, the result of heat and light acting on the pigment cells, 

 and, in other cases, the re-sult of what, for want of a better name, I 

 may call topical selection — that is, the selection by the animal 

 of its environment. Obviously, this environment would be a 

 cover or background which would enable the animal to escape 

 observation, as by that means many animal.'^, especially such as 

 are not possessed of great speed or great powers of flight, might 

 elude their enemies, or, if Carnivcia, might steal upon their 

 prey unawares. No doubt there is ; omething captivating in the 

 idea of a universal cause to which every change in the organic 

 world may be referred ; but it is surely contrary to the rules of 

 right reasoning to invoke the aid of a greater force than is 

 necessary to account for a given result. This is what the 

 Darwinist does, however, in order to explain ihe phenomena of 

 protective coloration and mimicry. It is well known, however, 

 and it has been pointed out by Dr. Wallace liimself, that certain 



