ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 175 



progression, play a regulating and not an intrinsic part. Their chief 

 importance may be in the grading of the individual component move- 

 ments to the temporary exigencies of the environment. 



Stomach of Ruminants.* — Erwin Schmidt gives a general account 

 of the ruminant stomach, and of its most important microscopic features 

 in its different parts. He then compares the stomachs of Hysemoschus 

 aqunticus, various species of Traguhis, Nanotragus, deer, and goat, 

 bringing out the remarkable unity of plan in all these types. The 

 Tragulid stomach shows a far-reaching affinity with those of Nanotragus, 

 deer, and goat. On the whole, the conditions exhibited by Hgsemoschus 

 are the simplest. The stomachs of llama and pig are also brought under 

 discussion in this useful comparative survey. 



Adrenal Secretion and Emotional Excitement.f — W. B. Cannon 

 brings forward additional evidence to show that the adrenal glands share 

 in the widespread subjugation of the viscera to sympathetic control. 

 Indirect proof was obtained from an excited cat with every sign of 

 sympathetic discharge, that the sympathetic impulses increase the secre- 

 tion of the adrenal glands. 



&' 



Iridescent Colours of Birds and Insects. J — A. Mallock discusses 

 the view of Michelson and of Walter that the brilliant iridescent colours 

 of birds and insects are, in most cases, due to selective reflection from an 

 intensely opaque material, and, in a few cases, to diffraction from a finely 

 striated surface. The author brings forward evidence in support of the 

 opposite conclusion that, in the majority of cases, interference of some 

 sort is the active cause ; although, in others, the possibility of selective 

 reflection is not excluded. The question really turns on the size of the 

 " grain " of the colour-producing structure. Is it comparable with the 

 wave-length of light or of molecular dimensions ? If the colours are due 

 to interference, the first supposition must be true ; but if selective 

 reflection is the agent, a comparatively small group of molecules may 

 cause selective reflection. A study of feathers, butterfly scales, beetles, 

 and flies, revealed the fact that the colour disappeared under compression, 

 and it seems probable, therefore,that interference of one kind or another 

 is the true cause of natural iridescent colours in all cases. 



Warning Coloration in a Chameleon. § — Cyril Crossland notes 

 that a chameleon, molested by a fox-terrier, tried to run away, but find- 

 ing this impossible, " at once turned round, opened its great pink mouth 

 in the face of the advancing foe, at the same time rapidly changing 

 colour, becoming almost black. This ruse succeeded every time, the dog 

 turning off at once." 



Variable Coloration of a Tree-frog.|| — E. G. Boulenger describes 

 Hyla goughi sp. n. from Trinidad, and comments on its rapid changes of 

 colour, which are probably unparalleled in any other Batrachian. The 



* Arch. Natur., Ixxvii. (1911) pp. 1-40 (3 pis.). 



t Proc. Amer. Phil. Soc, 1. (1911) pp. 226-7. 



t Proc. Roy. Soc, Section A, Ixxxv. pp. 598-605 (1 pi.). 



§ Proc. Zool. Soc. (1911) pp. 1066-7. 



II Proc. Zool. Soc. (1911) pp. 1082-3 (1 pL). 



