530 

NATURE 
[Jury 8, 1915 

Bay is the motherland of the Mannar pearl oysters. 
In a second chapter the author discusses first of all 
the limitations of the pearl-oyster habitat in Palk Bay. 
A second biological note contains the results of the 
author’s observations on the pearl oyster spat, and he 
distinguishes three stages of development of the pearl 
oyster larva and estimates that oyster larvae may be 
subject to current disposal for as long a period as 
fifteen days. In a third biological note the author 
details the results of his investigation on the parasites 
found in the oysters of the Tondi beds. 

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Alignment Charts: their Principle and Application 
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The Health of the Child. By Dr. O. Hildesheim. 
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Nature and Science on the Pacific Coast. Pp. xii+ 
302+ plates. . (San Francisco: Paul Elder 
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The Essentials of Agriculture. 
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and Co.) 
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(Boston and ‘London: Ginn and 
Co.) 1.25 dollars. 
A First Book of School Gardening. By A. Logan. 
Pp. vit151. (London: Macmillan and Co a Ltd.) 
Is. 6d. 
Exercises in Laboratory Mathematics. By A. W. 
Lucy. Pp. 245. (Oxford: At the Clarendon Press.) 
35. 6d. 
Arithmetic of Alternating Currents. By E. H. 
Crapper. Pp. vii+208. (London: Whittaker and 
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Alternating-Current Work. 
Pp. xxiv+415. (London: 
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Morals in Evolution. 
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Whittaker and Co.) 6s. 
By Prof. L. T. Hobhouse. 
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Masonry. By Prof. M. A. Howe. Pp. ix+160. 
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The Examination of Hydrocarbon Oils and _ of 
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The Internal Combustion Engine. 
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NO. 2384, VOL. 95] 
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CONTENTS. PAGE 
Emma Darwin and Her Circle. ..-...... 503 
GolloidiiGbemistry. 2 £ cs) ele een eed oe 504 
Geography as a Science ...... cha cotbren ven cers 504 
Musical Form and Development ....... + + 505 
OursBookshelf.:. . - =~.) /-0o MoeNCnen mn mane 506 
Letters to the Editor :— 
The Okapi.—Dr: 'C. Christy 7) 255 2 seme 506 
Testing Respirators.—W. P. Dreaper ...... 507 
Photograph of Mellish’s Comet. (Z//ustrated.)—H. E. 
Wiood .: .. -. ). 0 2Ou ge eee onan 507 
Bird Migration. —_Ed. Wilding Breech ete 508 
Mercury “Ripples showing Interference. (Zllustrated.) 
= 5. G) Starling <)ii 5 seen ee 508 
Man’s True Thermal Environment.—Dr. James 
Robert) Milne: .. 4.02) eine eee ne 508 
High Explosives. By George W. MacDonald. . . 508 
Science in the Service of the State, By Prof. F. G. 
Donnan, F.R.S. - 509 
Mammals of Eastern Waeeatarial pte (7ilus- 
trated.) By Sir H, H. Johnston, G.C.M.G., K.C.B. 510 
Organisation of Scientific Work in Todia.| 5 ia! 513 
Chi i Thad oo ac a one OG c 513 
Our epenomical ‘Column = — 
WhenMeteor (Season: vy urea 519 
Displacements of Enhanced Iron Lines at Centre of 
the: Sun’s ‘Disc’... Speer Sa ee 519 
The Maximum Brightness of Venus . Fae ys) 
Causes of Changes in the Rate of a Watch... . 519 
hevbritish) Science (Giild geese eee ee 519 
A Consultative Council in Chemistry. ...... 523 
The Research Defence Societyzuce-tr) (lee 524 
Ferromagnetism and the Az Transformation in 
IironteeBy Ex. C,H: C= eee een 525 
Recent Marine Researches) sues 526 
The Fiftieth Anniversary of the Worcester Bois 
technic) Institute; Mass: =) Seeueeeio a eeiee 526 
University and Educational Intelligence ..... 527 
Societiesiand Academies) > :) ene) ees) nea 528 
Booke Received =. . .) eyo ADM Aes 530 


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