;i6 



NATURE 



[September 20, 1S94 



employed could not be conducted any distance without en- 

 countering enormous induciive resistances, could be got over by 

 effectini; the transformation in the immediate neighbourhood 

 of the lamp. Since only condensers of small capacity and 

 inductance are required, a transrormer might be attached to the 

 lamp itself. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, June i\. — "On the Evolution of the Verte" 

 bral Column of Fishes." By Dr. H. Gadow, E.R.S., and Miss 

 E. C. Abbott. 



The following are a few of the more important points in the 

 paper : — Each skleromere lies wilhin the influence or range of 

 action of (wo successive myomeres. Taken as a whole, the 

 skleromere is "interprotovertebral," more correctly bi-protover- 

 tebral, because it is composed cf two successive sklerotomes, 

 namely, the ventral half of one and the dorsal half of a second. 



Consequently, the " resegmentation " or " neugliederung " is 

 brought about in a manner fundamentally different to that 

 hitherto supposed to have taken place. If \ and li mean two 

 successive sklerotomes, ii and i> their dorsal, a. and & their 

 respective ventral halve.'^, then the new skleromeie is composed 



of i-foand not of '- 



2 



The formation of a skleromere by the combination of alter- 

 nating dorsal and ventral halves of sklerotomes explains also 

 the presence of eight (four pairs) cartilaginous pieces, namelv, 

 basalia (so-called dorsal and ventral arches) and inierbasali,i 

 (so-called intercalary pieces) for each complele segment. 



Concerning the formation of centra or bodies ol ihe vertebra", 

 we distinguish : — • 



I. Choriiaciiitra, i.e. centra cut out of the full of the chordal 

 sheath, which itself has been strengthened by inv.ision of carti- 

 laginous cells from the skeletogenous layer. Chorda-centra are 

 possessed by all Elasmobranchs, potentially by Dipnoi and 

 Holocephali. 



II. Arrh-centra, i.t. centra formed by the skeletogenous 

 mass which remains entirely on the outside of the chordal sheath, 

 which latter takes no share in their formation : osseous Ganoids 

 and Teleostei. 



Chorda-centra and arch-centra represent two diflerent modes 

 of development, each starting from an acentrous condition. 

 This can be expressed as follows : — 



Chordal sheath remaining 

 entirely chordagenous. 



Chordal she.ith strengthened by 

 invasion of skelctogcn jus cells, 

 therefore with possibility of 

 chorda-cenlra. 



Dipnoi and Holocephali. 



Cyclostomala. 

 Cartilaginous Ganoids. 



Formation of Centra. 



Osseous Ganoitls, Teleostei. Elasmobranchs. 



ARCH-CE.srRA. 



ClIORDACKNTRA. 



The formation of chorda-centra being independent of ihc 

 arcualia explains how and why the number of "'centra" docs 

 not necessarily agree either with that of the arcualia or with 

 that of the Irunk-segmenL-, e.,^. Ilexanchus and tail of most 

 other Elasmobranchs. 



In .itiiia <al-a, the foilcenlnim, i e. Ihe posterior, archlcss 

 disk of a complete lail-verlebra, is lormed by the interdorsalia 

 and intervtntraliaof thesame sklerotome, while thc/»v«H////«;, 

 I.t. the arch bearing disk or anterior half is formed by the 

 basidorsals of the same sklerotome and the basiventrals of the 

 next previous sklerotome. The intermuscular septum runs 

 obliquely across the preccntrum, or, in other words, the pre- 

 centia are bi-protovertcbral or bi-myomeiic, but not the post- 

 centra. 



In f.tfiilesleus osseiis the combination of parts into one verle- 

 btal complex is superior to that of Amia, because each vertebra 

 Iwlong!, with its entire anterior half, to one, and with its posterior 

 half to the next following myomere. The vertebra- are now 

 truly bi-protoveitebral or bi-myomcric. 



Paris. 



Academy of Sciences, September lo.— M. Lccwy in the 



chair. — Truffles [Terjus) Uom Tunis and Tripoli, by M. Ad. 



Chatin. Trufiles have Ijeen received by the author from Tunis 



tieloDging to the species Tei/ezia Clavrryt. They seem always 



NO. 1299, VOL. 50] 



to occur in company with a herb called by the natives .Arong- I 

 Terfeis^ which is Hclianthemitm sasilifhruni^ Pers. {Cis/tts ' 

 scssilifloriis, Desf. ). Truffles similarly received from Tripoli are 

 classed as Terfezia Foudieri. — On the equations of mechanics, 

 by M. Wladimir de Tannenberg. — On Pfaft's problem, by M. 

 A. J. Slodolkievitz.^On another determination of the circle 

 derived from seven right lines and on some of its applications, 

 by M. Paul Serret.^On Diptera harmful to cereals ; observa- 

 tions from the Paris Entomological Station in 1S04, by M. Paul 

 Marchal. CcaJomya dtstriictor (Say) h.is been very prevalent 

 among wheat in the West. Oats have hitherto been considered 

 proof against Hessian fly, but a form of Cecidomya has ravaged 

 large districts in 1S94. It remains to be seen whether this fly 

 is a new species or only a variety of Cetidomya ii-'strtiit^v modi- 

 fied by the diflerence of food. Other pests noted which have 

 causeil seiious damage are the following : Cecidomya (Di/i'c . 

 trilici (Kirb.), Osniiis piisiUa (Meig.), Camarola /lavi! :• 

 (.\Ieig. ), which has not heretofore been considered as injurious 

 to cereals, and Elachiftera ,or>iuta (Meig.). — On the recent fall 

 of aeroliths in Greece, by M. C. Malt<;zos. 



BOOKS. PAMPHLETS, andSERIALS RECEIVED. 



Hooks. — An Introducii>>n to Physical Measurement^ : IV. F. Koht 

 rausch, translated by Waller and Procter, 3rd edition (Churchill). — A 

 Naturalist on the Prowl : '* Eha" (Thacker). — Primer of Hygiene ; Dr. K. 

 S. Reynolds (MacmillanV — Elements of Marine Surveying: Kev. J. L. 

 Robinson, and edition (Macmillan). — Theophrastus of Efesus on \Vind- 

 and on Weather Signs, tran>latcd. &c., by J. G. Wood (Stanford\ — Mii 

 ^ouri ftotanical Garden. Fifth Annual Report (St. L >iiis). — Municipal 

 'technical School and Municipal School of .-Xrt. Manchester, Session 1S94-5, 

 Syllabus (Manchester). —The Earth : E. W. Small (Melhuen). 



Pami'MLKTS. — Creameries and Infectious Diseases; Dr. J. J. Welpley 

 (BaiMii:rc).— The Cretaceous Kim of the Bl.ick Hills : L. F. Wan 

 (Chicagol. — Principes et Mtfthodes d'lttude de Corrtrlatijn Giologique at> 

 Moyen dcs Plantes Fossiles : L. F. Ward (Chicago). 



Sekiai.s. — Proceedings of the Society for Psyctiical Research, Part xxv-. 

 Vol. .\. (K. Paul). Uotanische Jahrbiic^erfiir Syslemalik. Pflanzenqeschichit 

 und Pllanzengeographie, Achtzehnter Band. 5 Heft and Xeunzehnler Band 

 2 and 3 Heft (Leipzig, Engelmann). — Journal of State Medicine, .-Xugus 

 (Renshaw). — ^Journal of the Franklin Instiiute. September (Philadelphia).— 

 Museum d'Histoire Natiirelle des Pays lias, tome xiv. Catalogue. system* 

 tique, &c. : F. A. Jenlink (Lcide, Brill). — Quarterly Journal of Micro, 

 scopical Science, .-Vugusl (Churchill). — Proceedines of the .\cadeiny_ 

 Natural Sciences of Philadelphia. i3j4. Part 1 (Philadelphia).— Insect Life, 

 \'o\. vi. No. 4 (Washington). —Journal of the Royal Honicuiturat Society 

 Vol. xvii. Parts 1 and 2 (117 Victoria Street). — Psychological Review 

 September (Macmillan). — Abstract of the Proceedings of the I.inneai 

 .Society of New Vo-k for the Year ending March 27, 1:04, No. 6 (NeiA 

 York). — American Historical Register, No. i (Philadetptii.i).— Economlt 

 Journal, .Sepieiiiber (Macmillan). 



I 



CONTENTS. p.^ci 



The Principles of Pure Mathematics. lly A. E. 



H. L . . I 



Text-Books on Organic Chemistry. I'.y W. A. T. . 



Practical Physics. I!y G. F. C. Searle 



Our Book Shelf:— 



Murchc : " Object Lessons in Elementary Science " . ; 



Canu : " Prtcis de Mcttlorologie Ei do^ciie " 1 



"Sach- und Orls-Veizeiclinis zu ilt-n mineralo- 

 gischen und gtologischen Arbciten von Gerbanl 



vom Ralh" 49''j 



Ri'iiti : " Elementi di Eisica " 49! 



Letters to the Editor: — 



Latiivtile by Ex-Meridian.- J. White 49. 



Magnetism (if Rock Pinnacles. — Lieut. -General I 



C. A. McMahon 49'| 



Aurora.- J. Shaw 1"' 



Bright Projections on Mars' Terminator. By W. J. S. 



Lockyer 



Notes ^ 



Our Astronomical Column : — 



The Scmi-Annual Variation of Meteors 5", 



Geologies and Deluges, liy Piof. Sollas, F.R.S. . 50. 



The International Geological Congress at Zuric.T . Si' 



The International Congress of Hygiene 51 



Science in the Medical Schools 5' 



Forthcoming Scientific Books ... 51 



University and Educational Intelligence .... -51 



Scientific Serials 5'i 



Societies and Academies . .... 5'! 



Books, Pamphlets, and Serials Receivtd 51 



