ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 37 



lens. The contraction of the internal muscles of the eye brings about a 

 relaxation of the zonula, which is stretched during accommodation-rest. 

 During accommodation the lens approximates to its most convex resting 

 form. In Cephalopoda the lens is in very close union with the delicate 

 envelopes of the bulb, by accommodative increase in the eye-pressure, 

 the lens is pushed forward, without change in its shape, farther from the 

 retina, and adjusted actively for near vision.' In Echidna the conditions 

 are the same as in ordinary Mammals. In the otter there is an enormous 

 development of the iris musculature, apparently assisting in the change 

 in the shape of the lens. 



Comparative Physiology of Vision.* — C. Hess finds that the eyes 

 of Eeptiles and Birds differ from those of other Vertebrates in various 

 ways, e.g. in having the ciliary processes closely nnited with the lens. 

 In accommodation the iris is pressed firmly by its circular muscles against 

 the front of the lens, and there is, during accommodation, no communica- 

 tion between the anterior and the posterior chamber of the eye. But a 

 drop of fiuoreszein put into the anterior chamber of the eye of diurnal birds 

 finds its way through a small opening in the ciliary ring into the posterior 

 chamber. This is a new anatomical fact. 



In Chelonians and some other Reptiles the ciliary ring is not homo- 

 geneous all round. There is a specially large ventral ciliary process from 

 which a strong muscle, hitherto overlooked, extends in a temporal direc- 

 tion. 



The ciliary ring of Selachians is much less divergent from that of 

 Amphibians than from that of Teleosteans. 



The brine-shrimp, Artemia salina, shows extraordinary sensitiveness 

 to slight differences of illumination. This is increased many thousand 

 times by keeping the animal in darkness for 20 minutes or so. Its 

 visual qualities resemble in some ways those of a completely colour-blind 

 man. When tried with two lights, it always swims towards the one which 

 is the less bright to the colour-blind man. Careful experiments on hens 

 gave no support to the view that birds have a red-green colour-blindness. 



Touch at a Distance.! — M. Kunz gives the results of numerous 

 experiments on blind people with reference to the cutaneous sensation 

 which he calls "touch at a distance." It is not found in all the blind, 

 nor is it confined to the blind. It is localized in the skin. Careful 

 experiments show that it has nothing to do with hearing. It is definitely 

 tactile, as the following facts suggest. It is lessened in a cold room, 

 doubled in a highly heated room ; it may be obliterated on one side by 

 using cocaine ; it is reduced by anaesthetics, like lysol, applied to the 

 body. Blennorhea and some skin-diseases (small-pox, measles, and 

 notably scarlatina) seem to cause this hyperasthesia of the skin. 



Reactions of Toads to Different Coloured Lights. J — Henry Laurens 

 has experimented with Bufo amerkanus and i?. /o^r/^/-/ as regards their 

 reactions to monochromatic lights of equal intensity. He finds that 

 sensitiveness to differences in wave-lengths is present in the skin of 



* SB. Phys.-Med. Ges. Wurzburg (1911) pp. 52-4. 



+ Comptes Rendus, civ. (1911) pp. 431-4. 



t Bull. Mus. Comp. Zool. Harvard, liii. (1911) pp. 253-302. 



