484 



SCIENCE. 



[N. S. Vol. XVII. No. 430. 



produced by a peculiar form of bar.bules. 

 There are no attenuated portions, and the 

 individual barbules overlay one another 

 like shingles. 



The iridescence is confined to the distal 

 exposed portion of the feather; the same 

 barb may have iridescent barbules distally, 

 and non-iridescent barbules proximally. 



The iridescent barbules have much more 

 pigment than the non-iridescent, and this 

 pigment is in the form of spherical gran- 

 ules of melanin, which fill cavities enclosed 

 by a thin transparent layer of keratin. 

 The non-iridescent barbules have the usual 

 rod-shaped pigment granules characteristic 

 of ordinary feathers ; these are irregularly 

 distributed in the keratin of the barbule 

 and are often fused more or less completely 

 into small masses. 



The spherical pigment granules lying 

 next to the transparent horn layer produce 

 a dispersion of incident light, and the un- 

 aided eye receives a mixture of great num- 

 bers of the spectra thus formed. 



On Anamniote Emiryos of the Chick: 

 Frank Eatteay Lillib, Hull Zoological 

 Laboratory of the University of Chicago. 

 The experiments described in this paper 

 consisted, first, in the destruction of the 

 head fold of the amnion between the thirty- 

 third and forty-sixth hours of incubation, 

 with a heated needle; second, a similar 

 operation on the tail-fold of the amnion, 

 immediately after its appearance. If the 

 head fold were completely destroyed with- 

 out injury to the embryo, the development 

 might proceed up to the age of at least five 

 days in normal manner, except for the 

 complete absence of the amnion back to the 

 hind limbs. In such cases the embryo lay 

 naked on the surface of the blastoderm, 

 to which it was attached in the same man- 

 ner as a shark's embryo by a very broad 

 somatic and splanchnic umbilicus. 

 The main conclusions were: 



1. The lateral folds of the amnion are 

 in part dependent on the formation of the 

 head fold. In the absence of the latter 

 they are neither so high nor so long as 

 usual, and they do not grow around the 

 embryo. The lateral folds of the amnion 

 must have the support of the head fold to 

 climb up, so to speak, around the body of 

 the embryo. 



2. The tail fold of the amnion has only 

 a limited independent capacity of growth; 

 in the absence of the head and lateral folds 

 it does not extend even as far forward as 

 normal. 



3. Similarly the head and lateral folds 

 of the amnion have a limited capacity for 

 growth; their backward extension is not 

 simply checked by the advancing tail fold ; 

 for, in the absence of the tail fold, these 

 end with a free border in front of the hind 

 limbs. 



4. The absence of the amnion has, at 

 least for a time, only a limited effect on 

 the development of the allantois. 



5. Inasmuch as the embryo may develop 

 quite normally to the stage of five days 

 without the amnion, it is obvious that the 

 functional significance of the latter must 

 be slight during this period. It yet re- 

 mains to be determined how far the embryo 

 may develop without the amnion. Cer- 

 tainly there is no good reason for assuming 

 that five days is the limit. 



6. There is a certain relation of interde- 

 pendence between the formation of the 

 amnion and the body wall. In the absence 

 of normal formation of the lateral folds 

 of the amnion, the closure of the somato- 

 pleure to form the body wall proceeds more 

 slowly than usual. 



The Newly Hatched Larva of Argulus 

 megalops: Chas. B. Wilson, Westfield, 

 Mass., State Normal School. 

 The most recent classification of the 



Copepods divides them into three classes: 



