468 THE ZOOLOGIST. 



smaller waves, and thus we get a light that is lacking in long 

 red waves, and overburdened with short blue waves. By trans- 

 mitted light the opposite effect is produced, and an excess of red 

 comes through to the eye. 



Every observation made on blue feathers supports this theory 

 of the "colour of small particles." The disappearance of the 

 light and colour in xylol and balsam is due to the fact that the 

 fluid sets up optical continuity ; and the cap becomes, so far as 

 its individual effect on light is concerned, a part of the balsam. 

 We cannot easily order the experiment, but it sometimes happens 

 when dealing with fragments of feathers that the balsam reaches 

 only a single surface of the cap (as when the cell is still intact, 

 but the outer sheath of the barb removed) ; and in this case 

 there is only a marked diminution of the colour, and not com- 

 plete disappearance. 



I now come to some of the strongest points in support of the 

 theory. Eclectuspolychlorus* a wonderful Parrot found only in 

 the Papuan Islands, shows a strange dissimilarity in the colours 

 of the sexes. The male is almost entirely a brilliant and nearly 

 optically pure green, with small areas of blue and scarlet. The 

 female is largely bright red, diversified with very slight washes 

 of blue and yellow. Eoughly speaking, the male is all green 

 and the female all red. Krukenberg has studied the actual 

 pigments of the feathers of Eclectus, and shows that these are 

 the same in both sexes, although the general effect is so different. 

 The pigments number only three, and are melanin (black), araroth 

 (red), and zoofulvin (yellow). 



A feather from the back of the male is green. The barb 

 consists of a solid core pigmented with black, a single layer of 

 cells with bright blue caps — exactly the same as those in the 

 Kingfisher — and an outer transparent sheath tinted with the 

 yellow zoofulvin. Here again the colour does not agree with 

 Dr. Gadow's statements, for the underlying melanin has nothing 

 to do with either the blue or the green (as may easily be tested 

 by slicing the barb with a sharp knife), and the zoofulvin, which 

 turns the blue colour of the cell-caps into green, is obviously 



* Perhaps this may be particularized as E. roratus for the male and 

 E. cardinalis for the female, but my remarks doubtless hold good for the 

 other forms of this Parrot. 



