488 



NA TURE 



[September 5, 1907 



The above involves a recognition of the variation of 

 vapour pressure with the hydrostatic pressure of the fluid 

 to which it relates ; an equation giving the mode of 

 variation is derived. 



A graphical solution of the osmotic-pressure equation is 

 given. 



June 13. — " .Some Points in the Devclopnunt of 

 Ophiothrix fragilis." Bv Prof. E. W. MacBride, 

 1--.R..S. 



The paper contained a preliminary report on the result 

 of researches on the development of the British Ophiurid 

 Ophiothrix fragilis. The eggs of this species are small 

 (o-i mm. in diameter) and opaque, and the development 

 until the completion of the metamorphosis occupied 

 twenty-six days. The full account of the research, which 

 will shortly appear in the Quarterly Journal of Micro- 

 scopical Science, will contain the first complete descrip- 

 tion of the formation of all the organs of an adult 

 Ophiurid from their rudiments in the Ophiopluteus larva. 

 In the preliminary account two points of special interest 

 are emphasised: — (i) the varying character of the early 

 development according to the conditions under which the 

 egg was fertilised ; and (2) the indications of metamerism 

 in the coelomic sacs of the larva. With reference to 

 (i), if the eggs were artificially fertilised, i.e. if the ovary 

 were removed from the body and the eggs shaken out 

 and then mixed with sperm, a larva resulted in which 

 there was a precocious formation of mesenchyme, so that 

 the blastula stage was practically solid ; this was succeeded 

 by an invagination in which the endodermic plate was 

 many layered. As a result, the gastrula had a wedge of 

 cells projecting into the gut which was slowly absorbed. 

 A similar wedge seems to be a normal feature of the 

 development of Ophiura brevis, according to Dr. Caswell 

 Grave. If the animals were allowed to spawn naturallv, a 

 hollow blastula was formed, and invagination was norrnal ; 

 in addition, at the anterior end of the larva a vacuolated 

 crest of cells was formed, which later disappeared. With 

 regard to (2), the ccelom on both sides of the larva be- 

 came divided into three somites. Of these, the middle 

 one on the left side gave rise to the hydrocoele, or rudi- 

 ment of the water-vascular system ; its fellow on the right 

 is the homologue of the " dorsal sac " or " madreporic 

 vesicle " of Asteroidea and Echinoidea, but in Ophiothrix 

 fragilis it sometimes assumes a form similar to that of 

 its left antimere, showing that the water-vascular svstem 

 was originally paired. 



P.4RIS. 



Academy of Sciences, Aujusf 26.— M. A. Chauveau in 

 the chair.— Study of the spectrum of the comet i<)oyd. 

 Peculiarities of the tail : H. Deslandres and A. 

 Bernard. The spectrum of this comet has been studied 

 by two methods, with and without a slit. The present 

 note gives an account of the results obtained working 

 without a slit. The spectrum shows bands in the yellow, 

 green and blue corresponding to hydrocarbons, and, in 

 addition, the characteristic ultra-violet band of cyanogen. 

 Differences were observed between the spectrum of the tail 

 and that of the head, but further observations are re- 

 quired to elucidate the exact meaning of these differences. 

 — Parthenogenetic developments in solutions isotonic with 

 sea water : Yves Delate. .All the principal salts of 

 sea water, employed separately, including the chlorides 

 of sodium, potassium, magnesium, calcium, the sulphates 

 of sodium and magnesium, and magnesium bromide, can 

 determine parthenogenesis of the eggs of sea urchins ; 

 these vary greatly in their effects, and the best solutions 

 for each are given in detail. One unexpected result is 

 noted : a pure solution of saccharose sometimes allows of 

 strong development of the egg. As regards the stage to 

 which It is possible to raise the eggs, the author has at 

 last been able to obtain true sea urchins furnished with 

 all the characteristic organs by a purelv chemical action. 

 —Propylene oxide : Louis Henry. It is known that 

 primary alcohols arise from the action of alkvl magnesium 

 compounds upon ethylene oxide, and in a p'revious paper 

 the author has shown that the symmetrical dimethvl- 

 ethylene oxide behaves differentlv. In the present com- 

 munication it is shown that methylethylene oxide, or 

 NO. 1975, VOL. 76] 



propylene oxide, resembles ethylene o.xide in its reaction 

 with ethyl-magnesium-bromide, normal methylpropyl- 

 carbinol being formed. — The ephemeris for the search for 

 the comet i9o7(J on photographic negatives : P. 

 Stroobant. — The root of the least modulus of an 

 algebraic equation : Leopold Fejer. — The theory of the 

 radiation of incandescent mantles : M. Foix. The con- 

 clusion is drawn from the mathematical investigation 

 given that the yield of light may be increased either by 

 diluting the cerium oxide in thorium oxide or by reducing 

 the thickness of the cerium oxide. The latter result has 

 been confirmed by experiment. — The probable formation 

 of thorianite and uranlnlte : B. Szilard. The amounts 

 of uranium and thorium in these two minerals are in 

 practically inverse ratios ; the proportion of uranium in 

 thorianite is the same as the proportion of thorium in 

 uraninite, and inversely. From this fact hypotheses are 

 deduced as to the mode of formation of these two 

 minerals. — The action of cold in the treatment of coffee 

 trees against the Indian borer {Xylotrechvs quadrupes): 

 Louis Boutan. The momentary cooling of the stem of 

 the tree by such a substance as ethyl chloride presents no 

 inconveniences from the point of view of the life of the 

 plant, and is sufficient to kill all the larvae in the interior 

 of the wood. The price of ethyl chloride, how ver, is too 

 high for any practical use to be made of the-.p results. — 

 A newly born hippopotamus at the menagerie of the 

 Natural History Museum, fed by goats : E. L. 

 Trouessart. The mother of the infant hippotamus had 

 always on previous occasions refused to feed her young. 

 In the present case the young anirqal was removed, and 

 has been successfully reared for eleven days by goats, eight 

 of whom serve as foster-mothers. — The mechanism of the 

 closing of the appendicular canal : R. Robinson. 



CONTENTS. PAGE 



Marignac's Collected Papers 465 



The Blood-Sucking Gnats. By R. N 466 



Commercial Organic Analysis. By T. A. H. ... 467 



Scientific Aspects of Photography. By C. J. ... 468 

 Our Book Shelf: — 



Milne : " Surgical Instruments in Greek and Roman 



'Times" 468 



Lundbeck : " Diptera Danica. Genera and Species 



of Flies hitherto found in Denmark " 469 



Letters to the Editor: — 



Radiation of Meteors. — W. F. Denning 469 



Experiment on the Rusting of Iron. — Geo. A. 



Watson 469 



The Explosion of Gases. (H/iislra/ai.) By L. B. . 470 



The Seventh International Zoological Congress . . 471 



Notes 473 



Our Astronomical Column: — 



Daniel's Comet, \i)oyd 476 



Solar Observations at Cartuja, Granada 476 



Discovery of Seventy-one New Variable Stars . . . . 477 



The Electrical Action of the Sun 477 



Micrometer Measures of Double Stars 477 



The May or Gorsedd Year in English and Welsh 



Fairs By Rev. John Griffith 477 



Kathode Rays and the Aurora. (I/liislraled.) By 



Dr. C. Chree, F.R.S 481 



Chemistry at the British Association 48a 



Geology at the British Association. By J. L. . . . 484 



Engineering at the British Association 485 



University and Educational Intelligence 487 



Societies and Academies 487 



