TRANSACTIONS OF THE SECTIONS. 101 



Thus, placing a mechanical interpretation upon colour, he considers the evidences 

 of (i) gain and (ii) loss of energy m the animal kingdom, and finally deals with 

 (iii) adaptation to environment and (iv) colour-distribution. 



I. Evidences of Gain of Energy. — Under this head the author includes those 

 changes of tint in hair Sec. which take place from youth to adult age. The change 

 is not only seen in man, but in the Primates and other orders of animals. Sexual 

 differences are tabulated, and it is shown that the fact of the male being most ab- 

 sorptive-coloured is indicative of its having more energy than the female. The 

 order is reversed among the fishes. 



II. Evidences of Loss of Energy. — Greyness accompanying old age in the animal 

 kingdom is taken as a proof of this ; greyness produced by disease and the change 

 one sees in certain fishes previous to putrefaction. 



III. Adaptation to Environment. — There is reason for thinking that the winter 

 change in the arctic fauna is induced by rigour of climate, and is protective 

 against that rigour. In dealing with adaptation as manifested in the lower orders 

 of life, he first proceeds to show that certain well-known cases of colour-change 

 among chemical salts produced by light and by heat are cases of adaptation to 

 environment. It is shown that the cases of adaptation in the lower orders of 

 animals are probably analogous, if not identical, to those among inorganic bodies. 



IV. Distribution of Colour. — In the lighter tint generally found on the abdominal 

 parts of animals, we have a colour localized which, in the arctic regions, is distri- 

 buted all over. It may be similarly induced and have to serve the same end. 

 Those parts are most absorptive-coloured, and presumably are the best radiators of 

 heat, where warmth andeconomy of heat is not very necessary, as, e. g., the pri- 

 maries and tails of birds, and the leg-flanks, manes, and tails of quadrupeds. Brown 

 horses have black manes and tails. 



On the Habits of the Pearly Nautilus (Nautilus pompilius). 

 By Dr. G. Bennett, F.L.S. 



The author said that the idea that Nautilus and Spirula are deep-water forms is 

 fallacious ; for though the Nautilus pompilius has rarely been met with, the shells 

 are often found on beaches in the Indian Ocean and South Pacific, where, he said, 

 he was not aware of any deep-water mollusk ever having been cast. On the 24th 

 of July, 1874, however, the ' Challenger ' exploring party netted a Nautilus in 

 about 320 fathoms of water off Matuka Island, and for some time kept it alive in a 

 tub to observe it habits. It propelled itself, after the manner of Cephalopoda, 

 " backwards," and each pair of its tentacles was found to have a definite and diver- 

 gent direction. The great depth at which the ' Challenger's ' specimen was cap- 

 tured was so opposed to experience that Dr. Bennett felt inclined to believe it was 

 netted by the trawl as it passed near the reef, or as it was floating at a slight depth. 

 It was noticed that the ' Challenger ' Nautilus attained locomotion by ejecting 

 water after the manner of the Cuttlefish. The paper described the air-chambers, 

 by means of which the fish descends or rises at will in the water ; the muscular 

 funnel, by the use of which it propels itself in any direction, regardless of currents ; 

 and concluded with a comprehensive and clear description of its peculiarities. 



On Biological Results of the North-German Exploring Expedition. 

 By Dr. Otto Einsch. 



In this paper Dr. Finsch pointed out the principal biological results of the North- 

 German expedition to Western Siberia. He divided the regions traversed into the 

 steppes, the mountains, the wooded region of the Obi, and the treeless " tundras " 

 north of 67° north latitude, and enumerated the most characteristic animals of each 

 region. Among the most important points were the occurrence of Himalayan and 

 Indian forms in the mountains near the Altai range, where such truly Arctic types 

 as the Reindeer were met with. 



