990 



SCIENCE 



[N. S. Vol. XXXI. No. ! 



The recent Antarctic explorations have pro- 

 duced a fair number of new Medusag, many 

 of which have well-marked and interesting 

 specific characters, but there are only about 

 three new genera. Probably, according to 

 Dr. Browne, none of them will remain pe- 

 culiar to the Antarctic when the ocean has 

 been more thoroughly explored. The littoral 

 Hydromedusffi of the Antarctic have not yet 

 been found in the Magellanic, South Austra- 

 lian and New Zealand areas ; it looks as if they 

 belong to an ancient stock which has long 

 been isolated from the rest of the world by 

 the Great Southern Ocean. As evolution is 

 proceeding more slowly in cold than in warm 

 regions, the characters of an Antarctic me- 

 dusa should be more primitive than those 

 from a warmer sea. Dr. Browne gives com- 

 parisons which in a number of cases seem to 

 sustain this view. Some very large scypho- 

 medusse are reported, including a Diplulmaris 

 with arms twelve feet in length. 



The lichen material brought back by the 

 expedition included some twenty-five species 

 and there are recorded from the Antarctic 

 continent and closely adjacent islands some 

 eighty-eight lichens. Of these thirty-eight 

 are confined to the region between 60° and 

 Y8° south latitude, as far as known. The 

 southern lichens do not present any new 

 genera and occur in small quantities con- 

 trasting with the abuiidance found in the 

 Arctic regions. Four species were found on 

 the peaks of the Antarctic volcanoes, Mts. 

 Erebus and Terror, and of these three are 

 also inhabitants of the Arctic regions. That 

 any indigenous organized object whatever 

 can exist on these gloomy volcanic peaks 

 covered with and rising out of eternal ice and 

 snow, seems almost miraculous ! 



The plates of this" volume are of the usual 

 high quality, and the whole character of the 

 work is such as would be expected from the 

 authorities of the British Museum. 



Wm. H. Dall 



Catalogue of the Lepidoptera Phatwnce in the 

 British Museum. Vol. IX., Noctuidas, 1910. 

 The present volume completes the account 



of the subfamily Acronyctinaj of the Noc- 



tuida3. It contains 725 species in 185 genera, 

 showing a total for the subfamily of 2,288 

 species in 385 genera. The volumes of this 

 series are appearing with gratifying rapidity- 

 We have only recently noticed the publication 

 of volume VIII. The present volume is on a 

 par with its predecessors in general plan and 

 execution. The table of genera for the sub- 

 family is again repeated with final additions 

 and corrections and will now become fully 

 available. 



Harrison G. Dyar 

 U. S. National Museum, 

 Washington, D. C. 



/ SPECIAL ARTICLES 



ON THE SPECTRUM OF MARS AS PHOTOGRAPHED 

 WITH HIGH DISPERSION ^ 



Let us recall that the solar spectrum, as 

 viewed by terrestrial observers, is composite. 

 Photospheric light, in passing out through 

 the gases and vapors of the sun's atmosphere, 

 is selectively absorbed, with the result that 

 many thousands of lines are introduced into 

 the spectrum. The transmitted light passes 

 down through the earth's atmosphere to the 

 observer, and the absorption by water vapor 

 and oxygen in the terrestrial atmosphere in- 

 troduces many hundreds of additional lines, 

 at definite points in the yellow, orange and 

 red regions. The observed spectrum of the 

 sun is in reality the spectrum of the sun plus- 

 the spectrum of the earth. The spectrum of 

 the moon, so far as our present problem is 

 concerned, is simply this sun-earth spectrum. 



The light from Mars is photospheric light, 

 which passes out through the sun's atmos- 

 phere, thence down through the atmosphere 

 of Mars to the planet's crust, where a certain 

 proportion is reflected out through the Mar- 

 tian atmosphere, and thence down through 

 the earth's atmosphere to the observer. The 

 so-called spectrum of Mars is in reality the 

 sun's spectrum plus Mars's spectrum plus the 

 earth's spectrum.^ Any water vapor and 



^Read at the April, 1910, meeting of the Na- 

 tional Academy of Sciences. 



= A little of the light would be reflected from 

 the atmospheric strata of various heights without 



