September 22, 1916] 



SCIENCE 



431 



type of lamp, the use of which, undoubtedly, 

 will increase the present number of observing 

 nights per month by at least twenty-five per 

 cent. 



The main part, an ordinary automobile head 

 light, is suitably mounted for directing in the 

 horizontal and vertical; the lamp is provided 

 with an ammeter, a small rheostat and a 

 switch. The whole, packed in a strong case, 

 weighs twenty-three and one half pounds. 



In order to obtain most nearly the maxi- 

 mum intensity of the light, it was necessary 

 that the lamp bulb be provided with a filament 

 concentrated to a degree not found in those on 

 the market. One of the lamp manufacturers 

 was induced to make the necessary designs 

 and experimental tests, and submitted a num- 

 ber for trial. 



At the present time all the lights of the sta- 

 tions surrounding the observer's station are 

 kept burning continuously from sunset to the 

 closing of the observations for the night. The 

 use of the dry cell was found practicable and 

 not too costly on the assumption that the pro- 

 posed lamp was to be kept burning throughout 

 the night. The trial of the newly designed 

 lamp by comparison with the present acetylene 

 lamp, however, proved the former so much 

 superior, that it was decided to have the lights 

 shown only on signal, flashed with one of the 

 new lamps by the observer, for the few min- 

 utes each time it is observed upon. This re- 

 duces very materially the consumption of cur- 

 rent and battery cost. 



The lamp, after being provided with two 

 additional bulbs, one for medium and one for 

 short distances, was tested by the Bureau of 

 Standards, with the following results : 



Apparent candle power, at a distance of 

 100 ft. Lamp with specially concen- 

 trated filament, gas filled, 6 volts, 2.5 



amp 250,000 



Automobile lamp, 6 volts, 1.8 amp 50,000 



Flash light lamp, 2.7 volts, .34 amp 6,000 



The candle power of the acetylene lamp now 

 used in the triangulation carried on by the 

 survey, measured under the same conditions, 

 is 1,500. 



E. G. Fischer 



XJ. S. Coast and Geodetic Survey 



SPECIAL ARTICLES 



LINKED MENDELIAN CHARACTERS IN A NEW 

 SPECIES OF DROSOPHILA 



In my cultures of a new species of Droso- 

 phila, tentatively called " species B," 1 several 

 mutants have recently appeared. They have 

 not all been tested fully with respect to their 

 linkage relations, but enough has been learned 

 to suggest some interesting possibilities when 

 considered in connection with the results of 

 Morgan and others on Drosophila ampelophila. 

 Three linkage groups have already been ob- 

 tained in my material, and five characters re- 

 main to be studied. Of the linkage groups 

 one is sex-linked and contains four characters, 

 the others are non-sex-linked and are composed, 

 respectively, of one and two characters. 



So far as the evidence goes, it indicates a 

 mode of inheritance in this fly entirely com- 

 parable with that in D. ampelophila, although 

 I have as yet been unable to determine whether 

 or not there is " crossing over " in the male, 

 because the only linked factors thoroughly 

 studied (aside from the sex-linked group) are 

 completely linked and give no crossing over 

 in either sex. 



The most interesting feature of the results, 

 as they stand at present, is the apparent corre- 

 spondence between certain mutant characters 

 in this species and in D. ampelophila. Four 

 of the characters I have obtained show this 

 correspondence. One of them (" confluent ") 

 has already been recorded. 1 It is a dominant, 

 non-sex-linked character, and has a lethal 

 effect when flies are homozygous for it. Its 

 counterpart in ampelophila is an almost exact 

 duplicate in appearance, and apparently has the 

 ' same peculiarities in genetic behavior. There 

 seems to be little doubt that these characters 

 are actually alike in the two species. The 

 other three are "black," "yellow" and 

 " forked." Black has only been studied enough 

 to tell that it is not sex-linked; and since there 

 are two or three factors in ampelophila that 

 give a melanistic effect, there is some doubt as 

 to which, if any, is really comparable to the 

 one I have found. But with respect to yellow 

 and forked the case is different, for they not 

 only correspond exactly in appearance, but 



i Metz and Metz, ' ' Mutations in Two Species of 

 Drosophila," Amer. Nat., 1915. 



