Febeuaby 3, 1911] 



SCIENCE 



171 



that, within definite and often very wide limits, 

 it does not depend on the absolute amount of the 

 various food substances, but upon their respective 

 degrees of concentration. As we have already 

 stated, the production of flowers follows a rela- 

 tive increase in the amount of carbohydrates 

 formed in the presence of light, as compared with 

 the inorganic salts on which the formation of 

 albuminous substances depends." The various 

 modifications of flowers are due to the fact that 

 a relatively too strong solution of salts is sup- 

 plied to the rudiments of these organs. As a 

 general rule every plant form depends upon a 

 certain relation between difi'erent chemical sub- 

 stances in the cells and is modified by an altera- 

 tion of that relation. 



Vernon''" cites some interesting eases in 

 which changes of diet have apparently pro- 

 duced results in accordance with our law. 



John Hunter observed a most marked thicken- 

 ing and hardening in the stomach of a gull 

 (Larus tridactylus) which had been fed for a 

 year on grain. It is stated by Dr. Edmonston 

 that a similar change takes place under natural 

 conditions every year in the stomach of the com- 

 mon herring gull ( Larus argentatus ) . Thus in 

 the Shetland Islands this bird feeds in the winter 

 on fish, but in the summer frequents the corn- 

 fields and feeds on grain. Dr. Edmondston has 

 also noticed a somewhat similar change in the 

 stomach of a raven which had been fed for a 

 long time on vegetable food. Again, Menetries 

 found that in an owl {l^irix Oallaria) the effect 

 of vegetable diet was to change the form of the 

 stomach and make the inner coat leathery. 



The converse experiment of feeding graminiv- 

 orous birds on a flesh diet has been made by 

 Dr. Holmgren. By feeding pigeons on meat for 

 a considerable time, he found that the gizzard 

 gradually acquired the qualities of a carnivorous 

 stomach. Again Delage fed a fowl for three years 

 on meat, and found that the muscular substance 

 of its gizzard was considerably decreased. All 

 these results, though apparently so unequivocal, 

 have not passed unchallenged; for G. Brandes," 

 who fed both flesh-feeding birds on grain, and 

 grain feeders on flesh, states that he was unable 

 to trace any adaptation to the altered conditions 

 in either case. 



"Klebs, " Kunstliche Metamorphosen," 117. 

 " " Variation in Animals and Plants," 295 , 

 1903. 

 " Hiol. Centralblatt, 16, 825. 



Since these alleged changes are directly 

 in line with the cases previously quoted, of 

 the changes in butterflies and bog plants, 

 it seems probable that the negative results 

 are due to error. It is very desirable, how- 

 ever, that this point should be settled defi- 

 nitely one way or the other. 



A very complicated case of the effect of 

 the environment, and one which I shall not 

 attempt to account for, is cited by Poul- 

 ton.^s 



Entirely new light upon the seasonal appear- 

 ance of epigamic characters is shed by the recent 

 researches of C. W. Beebe,*" who caused the scarlet 

 tanager {Piranga erythro7nelas) and the bobolink 

 (Doliohonyx oryzivorus) to retain their breed- 

 ing plumage through the whole year by means of 

 fattening food, dim illumination and reduced 

 activity. Gradual restoration to the light and 

 the addition of meal-worms to the diet invariably 

 brought back the spring song, even in the middle 

 of winter. A sudden alteration of temperature, 

 either higher or lower, caused the birds nearly to 

 stop feeding, and one tanager lost weight rapidly 

 and in two weeks moulted into the olive-green 

 winter plumage. After a year, and at the begin- 

 ning of the normal breeding season, " individual 

 tanagers and bobolinks were gradually brought 

 binder normal conditions and activities"; and in 

 every case moulted from nuptial plumage to 

 nuptial plumage. " The dull colors of the winter 

 season had been skipped." The author justly 

 claims to have established " that the sequence of 

 plumage in these birds is not in any way pre- 

 destined through inheritance . . .," but it may 

 be interrupted by certain factors in the environ- 

 mental complex. 



SECRETIONS 



Under physiology and medicine mention 

 has previously been made that many or- 

 ganisms give rise to products which are 

 toxic to the organism and which must be 

 removed. Brunton'^" points out that "an 

 excessive quantity of their own products is 

 usually injurious to cells and too much 

 alcohol will stop the growth of yeast. At 



" " Darwin and Modern Science," 297, 1909. 



*T/ie American Naturalist, 42, 34, 1908. 



™ " Darwin and Modern Science," 174, 1909. 



