54 



NATURE 



[May 15, 1890 



Taking the Pkuronectidcc as a whole, we certainly get a 

 division into dextral and sinistral groups, which might be 

 supposed to be the result of a " like to like " segregation at an 

 early period. The following table of the sub-families, compiled 

 from Messrs. Jordan and Goss's excellent work on these fishes, 

 illustrates the point : — 



{\) Hippoglossincv : normally dextral, except the tropical 

 species, which are sinistral. 



(2) Pleuronedina : sinistral flounders. 



(3) Oncoptei-iitce : dextral. 



(4) PlatessincB : dextral, but Platichthys stellatiis is frequently 

 sinistral. 



(5) Soleina; : dextral soles. 



(6) CyttoglosstHiV : sinistral soles. 



But how comes it that the tropical flounders are nearly all 

 sinistral, while the Arctic and Antarctic ones are chiefly dextral ? 



It would be interesting to know more of the reversed aber- 

 rations which occur. Platessa flesus van passer (Linn.) is a 

 reversed form, and Day records reversed aberrations of Solea 

 solea, Pleuronectes rhombus, and P. maximus, while others have 

 been noted by various writers. T, D. A. Cockerell. 



West Cliff, Custer Co., Colorado, 

 April 25. 



Variation in the Nesting-Habits of Birds. 



In connection with T. D. A. Cockerell's letter, re the 

 nesting- habits of the blackbird in Colorado, it may be of 

 interest to note that in the grounds around our residence about a 

 fortnight ago, I discovered the nest of a blackbird {Mcriila vul- 

 garis) built upon the ground close to a boundary wall about five 

 feet high. The bottom of the nest is resting on the ground, 

 but there is some trailing ivy growing around — but not on the 

 wall — which supports it at sides and partially obscures it. There 

 is a public road on the other side of the wall and the noise of 

 considerable traffic. There are many suitable trees, bushes, 

 and shrubs, all around, some of which have been utilized by 

 other blackbirds — indeed, there is a tree within a few feet of 

 the nest, which would have been suitable but for the chances of 

 observation from the road. Thos. Swan. 



Bankplace House, Leslie, Fifeshire, Scotland, May 7. 



Doppler's Principle. 



In answer to a correspondent who has met with a difficulty in 

 the consideration of Doppler's principle, I may say that J think 

 I fairly solved the difiiculty in a paper delivered last year before 

 the University College Chemical and Physical Society. In 

 cases (i) and (2) of your correspondent, viz. approach or recession 

 of observer, source and medium being at rest, the correct formula 



is n' = n ^ ; and in cases (3) and (4), viz. approach and re- 



a 



cession of source, observer and medium at rest, it is n' = n — ?^ - 



a ^ V, 

 n = the new, and « the old frequency of vibration" of the note 

 heard. It should be remarked, however, that in all practical 

 cases, the two formulae give very nearly the same result ; but if 

 the velocity v is very great, the case is entirely different. Suppose, 

 for instance, in cases (i) and (2) that v = velocity of sound a, then 

 n = 2« for approach, and o for recession of the observer. The 

 correctness of these results is obvious without the aid of any 

 formula. Again, in cases (3) and (4) suppose v = a, then 



n' = oc for approach, and - for recession of the source of 



2 

 sound. The effect of an infinite number of waves striking the 

 ear at the same moment would be simply that nothing would be 

 heard. It would be interesting to notice the change in pitch of 

 the whistle of a rifle-bullet passing near an observer. Ganot's 

 formula is correct for cases (i) and (2), and Prof. Everett's for 

 cases (3) and (4) ; the proofs are very simple, and may be easily 

 thought out. When the observer and the source of sound both 

 move, the two formulae should be applied separately when a 

 very accurate result is desired. These conclusions have been 

 confirmed by Dr. Fison, of University College. I had not con- 

 sidered the effect of the motion of the medium, but it appears 

 to me, after a little reflection, that this would increase or diminish 

 the velocity of the sound, and the wave-length, in the same pro- 

 portion, leaving the pitch unaltered ; the velocity of the medium 

 should therefore be added to or subtracted from a in the formula. 

 University College, May 5. E. P. Perman. 



" Index Generum et Specierum Animalium." 



Naturalists have long needed a reference book to the 

 names of genera and species. Such a want has already been 

 partially supplied by Agassiz, Bronn, Morris, Marschall, Scud- 

 der, Waterhouse, and others— only Bronn and Morris having 

 attempted palaeontological species— but no one book including 

 references to all names given to living and fossil animals has yet 

 been attempted. Botanists, more fortunate, will soon possess 

 Daydon Jackson's index to flowering plants. The idea has 

 therefore suggested itself to me to begin at the end of June next, 

 such an "Index Generum et Specierum Animalium," taking 

 the following rules for guidance : — 



(1) The earliest reference is to date from the twelfth edition 

 of Linnaeus, 1766, 



(2) The last reference to close with December 31, 1899. 



(3) The names of genera and species to be given in a single 

 alphabetical sequence, and accompanied by a reference to the 

 original source. 



(4) The names of species of each genus to be also quoted in 

 alphabetical order under that genus. 



(5) No attempt at synonymy to be given ; but, to assist 

 reference, the various genera in which a species has from time 

 to time been placed, to be indicated under that species'. 



(6) Pre-Linnaean names to be quoted as founded by the 

 author first using them after 1766 -.—e.g. Echuiocorys, Leske, 

 1778 {ex Klein, 1734). Should a pre-Linn^an species or genus 

 have been re-named after 1766, before the post-Linnaean use of 

 that pre-Linnsean name, the new name is to stand. [References 

 will be given to Artedi, Brisson, and Scopoli, in accordance 

 with British Association rules.] 



Among the many offers of assistance, that of Prof. Flower, 

 F.R.S., Dr. Giinther, F.R.S., and Dr. Henry Woodward, 

 F.R. S., who have promised the necessary space for the storage 

 of the MS. in the Natunl History Museum, is most valuable, 

 as it practically ensures safety from fire, and renders the MS. 

 easily accessible to those wishing to consult it while still im- 

 perfect. 



The contribution of inaugural addresses, theses, or other 

 publications difficult to obtain, would be of great assistance; 

 and, after use, such pamphlets would be handed over to the 

 library at the Museum. 



Any suggestions for the improvement of this plan, before the 

 commencement of the undertaking, would be gladly received 

 and carefully considered. 



Appended is a rough outline of the scheme : — 

 [cordatus -a, -um] 



Amphidetus (Penn.) Diib. and Koren, Zool. 



Bid. 285 



\v. Echinus] 



Amphidotus (Penn.) E. Forbes, Brit. Starf. 



190, fig 



\y. Echinus] 



Echinocardium (Penn.) J. E. Gray, Cat. R. 



Ech. 43 



\v. Echinus] 



Echinus, Pennant, Brit. Zool. iv. 58, xxxiv. 



2, xxxvi. 2 



\v. also Amphidetus, Amphidotus, 

 Echinocardium, Spatangus] 



Spatangus (Penn.) Flem. Brit. Anim. 480 ... 1828 



\v. Echinus] 



Cordia, Stdl, Hem. Afric. iv. 78 Hem. 1866 



[albilaterata, peragrans.] 

 Cordienia, A. Rouault, B. S. geol. France, v. 207.. Gast. 1848 

 [biaritziana, iberica, palensis, pyrenaica, 

 all noni. nud.'\ 



Charles Davies Sherborn. 

 540 King's Road, London, S.W. 



1844 



1841 



1855 



1777 



" The Anatomy of the Frog." 

 In your notice of the above work, in Nature of the 8th 

 inst., you are pleased to express a favourable opinion of the 

 wood engravings. As the heading of the article might lead your 

 readers to imagine that these, in addition to the coloured plates, 

 were all executed by Hofmann, of Bavaria, I think they, as 

 well as yourself, will be pleased to know that all the new blocks, 

 numbering upwards of one hundred, were engraved by 



172 Strand, London. T. P. CoLUNGS. 



