36 



HARD 1VICKE ' S S CIE NCE - G SSI P. 



"Cybele Britannica" (1847-1859), not only did for 

 British plants what Alphonse De Candolle has done 

 for those of the world in his " Geographie Botanique" 

 (1855), but anticipated many of the principles of that 

 work. Leaving unmentioned much important matter 

 in the pages of periodicals such as the " Phytolo- 

 gist," the "Journal of Botany," the "Gardener's 

 Chronicle," and Science-Gossip, I will conclude this 

 list of authorities with the name of a great work still 

 in progress, the "Genera Plantarum " of Mr. Bent- 

 ham and Sir Joseph Hooker. 



There are, of course, many other important works 

 published abroad, besides special papers, &c, of 

 English authorship ; I shall even refer to others in 

 my research into the history of Thalictrum ; but these 

 are, I think, those most generally important in the 



history of British Botany. 



G. S. Boulger. 



ON THE COLOURS OF ANIMALS, AND 

 THE ARRANGEMENT OF PIGMENT IN 

 LEPIDOPTERA. 



By Alexander M. McAldowie, M.B., CM. 



ALTHOUGH limited to a few spots in man and 

 a few of the higher vertebrata, and altogether 

 absent in some of the lowest forms of animal life, 

 pigment is of almost universal occurrence in the 

 zoological kingdom. We gaze with wonder at the 

 dazzling splendour of the tropical birds and butterflies 

 which adorn our museums, and we admire even more 

 the softer beauty of the fauna of more temperate 

 regions, yet all this variety of tint is due to the 

 deposition in various parts of the body of colouring 

 matter, the nature and uses of which are as yet in 

 many instances but imperfectly understood. 



In some cases the use of pigment is to protect the 

 deeper tissues from the bright glare of the sun by 

 absorbing the rays of light. This is its function in 

 the eye, where it prevents the rays from being re- 

 flected back on to the retina and interfering with 

 vision. In most animals, however, pigment is present 

 for the purpose of enabling them to conceal them- 

 selves from their enemies or their prey ; the colour of 

 the animal, as a rule, bearing more or less resemblance 

 to that of the soil, herbage, or foliage in which it 

 lives. This is very strikingly seen in the "leaf" 

 insects, where the likeness is so close as to merit the 

 appellation of "protective mimicry." It may also be 

 observed in the eggs and young of birds which nidifi- 

 cate on the ground. 



Some animals possess the power of changing their 

 colour in a certain degree and assuming that of the 

 surrounding , medium. We have only to recall the 

 story of the chameleon in illustration of this. It 

 occurs in several reptiles, batrachians, and fishes.* 



* See an interesting note on the Angler Fish in Science- 

 Gossip for July. 



Many species of cuttle-fish can change their colours 

 rapidly under irritation or excitement. In birds and 

 mammalia, however, change of colour takes place 

 much more slowly, and is produced by shedding the 

 feathers or hair. This takes place at certain seasons ; 

 during the breeding season more especially, also in 

 the winter. The former is seen in the ruff and many 

 other birds, the latter in the ptarmigan, ermine, hare, 

 and others. The minnow, stickle-back, and several 

 other fishes exhibit bright iridescent tints during the 

 spring time. 



While noticing the uses of colouring matter in the 



Fig- 33. — Pigment-cells from the Tadpole. 



Fig. 34. — Pigment-cells still 

 cohering, from the choroid ; 

 mag. 370 diameters (after 

 Heule) ; a, nucleus. 



Fig- 35- — Ramified pigment- 

 cells, from the tissue of the 

 choroid ; mag. 350 diameter 

 (after Kolliker). 



animal kingdom, it is interesting to observe the 

 difference between animals and plants in this respect. 

 The colours of flowers are now understood to have 

 reference only to the visits of insects.* 



Pigment exists in the form of minute granules 

 deposited in the connective tissue corpuscles or the 

 epidermic or epithelial cells. The pigment-cells of 

 connective tissue are usually of a stellate or ramified 

 form (fig. 35), containing numerous processes. The 

 nucleus of the cell remains colourless, and, as a rule, 

 the ends of the processes contain no pigment. Briike 

 and Buchholtz have observed movements in the stel- 

 late pigment-cells of batrachians and fishes. The 



" Flowers," by Dr. Taylor, p. 14. 



