218 



SCIENCE 



[N. S. Vol. XXVI. ICo. 659 



females raised from isolated mothers in the 

 greenhouse. The matings and results were as 

 follows, the letters showing the color char- 

 acterS' which were visible: 



1. ?E(redpar.)X ,?EG(redpar.) {?; ^^'d^.^^^a green. 



2. 9 GE (green par.) X 3' G (green par.) .] All green. 



3. 5 E (red par.) X ^ G (green par.) -{ No eggs hatched. 



4. 9 GE (green par.) X ^ EG (red par ) {^; """erafgreen. 



Only a small proportion of the eggs hatched, 

 but the results, though meager, indicate the 

 possibility that color inheritance may here be 

 Mendelian, and that a further study of it 

 may throw light on the problem of sex in- 

 heritance. 



The coloration of the sexual generation, 

 however, shows that either one or the other of 

 two conditions must probably exist: (1) All 

 of the egg-ancestors and therefore all of the 

 parthenogenetic individuals, as well as the 

 males and females, are sex-hybrids as well as 

 color-hybrids, and the factors which determine 

 sex dominance also determine color domi- 

 nance, possibly by virtue of some structural 

 correlation of the two characters. (2) There 

 are green hybrid strains which produce red 

 females and red hybrid strains which produce 

 greenish-brown males, while the red strains 

 which produce red females may be pure reds 

 and the green strains which produce green 

 males may be pure greens. 



The first of these suppositions, which alone 

 could account for the conditions found in the 

 star cucumber aphid, where parthenogenetic 

 mothers of either color produce both red males 

 and green females, and in the goldenrod aphid 

 where the brown parthenogenetic mothers pro- 

 duce both green males and brown females, 

 seems much more likely to be true for all. 



In the following table the possibilities for 

 the star cucumber aphid are shown imder I., 

 and those for the Oenothera aphid under I. and 

 II. combined. (The color scheme must be 

 reversed for the star cucumber aphid, G?, JiS.) 

 In both, the dominance of sometimes one color, 

 sometimes the other in the parthenogenetic 

 generations is a subject for investigation. It 

 may be conditioned by the immediate ancestry 

 of the gametes. 



Gametes 



Parth. 

 Gen. 



Sexual 

 Gen. 



Gametes 

 ,G3'sp. 



B? stG)-^ ^ElGXE^egg 

 G ,? egg 



jSG $ ^Gm^ $ G{R)<i^<^,p, 



-cTG- 



-Se- 



-G5'sp.(?) 

 -E ? egg 



In the goldenrod aphid, if we consider the 

 parthenogenetic forms as essentially female, 

 correlation of color with sex (B ? and Gd"), 

 and selective fertilization would account for 

 the observed relation of color to sex. 



The second, and less likely but neverthe- 

 less interesting, possibility for the QUnothera 

 aphid involves the question whether a zygote 

 can be pure as to the sex character, or uni- 

 sexual. The chief point to be investigated by 

 experiment, in addition to the study of color 

 inheritance in cross-breeding, is whether in 

 this aphid both males and females come from 

 the parthenogenetic progeny of each egg-an- 

 cestor, or in some cases (G c?) only males, and 

 in others (R ?) only females. To test this 

 possibility it would be necessary to carry many 

 families through from the egg to the follow- 

 ing sexual generation, and very likely to re- 

 peat the experiment several times. 



A large series of experiments in cross-breed- 

 ing to test the color inheritance has been 

 planned by the author for next year, and this 

 note is published in the hope that some one 

 may be interested to undertake experiments 

 along the same line. 'N. M. Stevens 



Beyn Mawr C0L1.EGE, 



Beyn Mawe, Pa., 



June 8, 1907 



A COLOE SPOET AMONG THE LOCUSTID.E 



Theee are various sports among animals 

 that are so rarely observed and so little under- 

 stood as to seem to render it desirable that 

 every occurrence should be recorded. One of 

 these is the occasional substitution of pink 

 for green color among the Locustidse, which 

 has been recorded perhaps a dozen times. It 

 is to be hoped that repeated notices of their 

 capture may call the attention of physiologists 

 to them, and in time elicit a satisfactory ex- 

 planation of the phenomenon. A specimen of 



