220 SUMMARY OF OUBKENT RESEARCHES RELATING TO 



Blue Colour of Animals.* — Prof. F. Leydig says that a blue 

 granular pigment is rarely found in animals ; in the crayfish, for 

 example, there are blue crystals. The blue colour is more often due 

 to interference, owing to the presence of lamellae, or to the fibrils 

 of connective tissue, as in the tapetum fibrosum of the eye of 

 Ruminants ; the corium of the living larva of Pelohates fuscus is 

 similarly blue. A dull material overlying black pigment produces 

 blue, as in the case of blue eyes, which are due to the uvea shining 

 through the non-pigmented iris, and in some frogs. Dark chromato- 

 phores have a like efiect, as has too the swelling of the corium 

 consequent on the filling of the lymph-spaces. 



In conclusion, the author discusses the tegumentary secretions, 

 which are of various colours, and which can be washed away ; an 

 example is to be seen in the celestial blue colour of the abdomen of 

 Lihellula depressa, and, perhaps, the "bloom" of the pupa of the 

 Apollo butterfly. On the other hand, the colouring matter may be 

 in cells of the epidermis, as is the case with the rosy colour of Tetrao 

 urogallus, and can then, of course, only be removed after the destruc- 

 tion of the tissue which contains it. 



Perception of Brightness and Colour by Marine Animals.t— 

 Herr V. Graber has made some further experiments on marine 

 animals with the divided box already used by him. He finds that the 

 common star-fish is an eminently leucophilous or light-loving animal, 

 for the bright division of the box always contained 2*2 as many 

 individuals as the dark ; they avoid red, or are erythophobes, three 

 times as many seeking a dark-blue compartment. The common 

 jelly-fish {Medusa aurita) was neither specially sensitive to bright- 

 ness or to colour ; but it is possible that the results might be different 

 with larger aquaria. Idotea tricuspidata is very sensitive to light at 

 the maximum differences in brightness, for 6 • 3 as many individuals 

 sought the white as the dark compartment ; but they are quite in- 

 sensitive to less marked differences. They object to red and like 

 blue. Gammarus locusta does not seem to be affected by light or 

 shade; Bissoa odona dislikes the dark, and is sensitive to less 

 marked distinctions ; it again, in the proportion of 103 to 2, liked 

 blue and avoided red. Gasterosteus spinachia, like fresh-water fishes, 

 prefers darkness in the proportion of 78 to 6, and Syngnathus acus 

 gave somewhat similar results. 



B. INVERTEBRATA. 



Colouring Matters of the Integument.^ — M. P. Girod has in- 

 vestigated the chlorophyll-pigment of Hydra viridis, the pigment of 

 the skin of Cephalopods, and the ink-bag of these molluscs. 



The author is of opinion that the chlorophyll of green Hydrse 

 plays an important part in their economy, by furnishing them with 



* Zool. Anzeig., viii. (1885) pp. 752-8. 



t SB. K. Akad. Wiss. Wieii, xci. (1885) p. 129. See Naturforscher, xviii. 

 (188.5) pp. 48G-7. 



X Comptcs Eendus, ci. (1885) pp. 1371 4 (Report ou Prize Easay). 



