292 



SCIENCE. 



[N. S. Vol. XI. No. 269. 



It is evident that ia the Tonga Group, 

 which is a very extensive area of elevation, 

 the recent corals have played no part in the 

 formation of the masses of land and of the 

 plateaus of the Tonga Ridge, and that here 

 again, as in the Society Islands and Cook 

 Islands, both also in areas of elevation, they 

 are a mere thin living shell or crust grovF- 

 ing at their characteristic depths upon plat- 

 forms which in the one case are volcanic, 

 in the other calcareous, the formation of 

 which has been independent of their growth. 



We expect to leave for the Ellice, Gilbert, 

 and Marshall islands as soon as we can coal 

 and refit. 



A. Agassiz. 



TEE OCCURRENCE OF APT0S0CHR03IATIS3I 

 IN PASSERINA CYANEA.* 



The following remarks upon the Aptoso- 

 chromatism of Passerina cyanea, although 

 of insufficient importance to establish the 

 phenomenon of color change without moult 

 as a constant occurrence in the species, are 

 conclusive enough, I am convinced, to 

 prove the possibility of such a change, and 

 are merely offered as such for what they 

 may be worth. 



Individual error and dogmatism have 

 greatly retarded honest effort in this most 

 important branch of ornithological science. 

 It is a singular fact that certain individuals 

 have conceived the idea that a feather once 

 having passed its premature condition is 

 utterly disconnected with the vital system 

 of the bird, and such individuals cling to 

 this belief with a tenacity wonderful to be- 

 hold. They do not tell us, by the way, 

 how it is that certain species of birds lack- 

 ing external sebaceous glands manage to 

 present as bright plumage as their allies so 

 provided. Doubtless they may attribute 

 the presence of oily matters upon the sur- 

 face of the feathers of those species in 



* Read before the Nuttall Ornithological Club of 

 Cambridge, Mass., June 5, 1899, with exhibition of 

 the bird worked upon. 



which these glands are wanting to osmotic 

 action ; but admitting this, why not admit 

 Aptosochromatism ? 



In his article on alleged changes of color 

 in feathers (Bull. Am. Museum Nat. Hist. 

 1896), Dr. Allen compares a feather to a 

 green leaf, which when once formed, can- 

 not extend its growth to repair any injuries 

 which may arise from insects, etc. This 

 simile might well be carried yet farther and 

 to better advantage. When the later sum- 

 mer or earlj^ fall approaches, certain leaves 

 undergo a complete change in color, result- 

 ing in the beautiful colors of our Septem- 

 ber and October woods. The history of the 

 underlying phenomena of autumnal col- 

 oration in leaves is very obscure, yet no one 

 doubts the occurrence of the change for an 

 instant. So it is with Aptosochromatism — 

 the individual feathers undergo in many 

 cases complete color changes, and although 

 the underlying processes of these changes 

 may be obscure, the fact of their presence is 

 to ray mind undeniable. 



At the present time Aptosochromatism 

 has not progressed far enough to encourage 

 one to take up in detail the systematic oc- 

 currence of the color change in our species 

 of native birds. It seems evident that for 

 the present, attention should rather be de- 

 voted to endeavoring to demonstrate its 

 fundamental principles, without which no 

 science is firm, plainly evident as may be 

 its happening. 



Passerina cyanea, apart from its seasonal 

 fall moult by which the plumage acquired 

 in the spring is changed for the duller garb 

 of the fall, doubtless exhibts two forms of 

 Dichromatism, a term whose proper place, 

 I hope, is now recognized as the funda- 

 mental term for the complex phenomena of 

 double coloration. As I shall direct my at- 

 tention toward proving that Aptosochroma- 

 tism is concurrent in the species, and Ptoso- 

 chromatism in the present paper will play 

 an inconspicuous part. Both are compre- 



