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POPULAR SCIENCE REVIEW. 
habitation of the larva is a mine, which is made in the leaf by eating out the 
soft green substance (parenchyma) between the upper skin (epidermis) and 
the framework of the leaf, laying the framework bare, but leaving the epi- 
dermis intact, except at the point where (he supposes) the larva enters the 
leaf. At this point the wound heals up and forms a lenticular scar twenty- 
five hundredths of a millimeter in length, and fifteen hundredths of a milli- 
meter in breadth, raised a little above the general surface of the leaf. The 
epidermis which covers the mine becomes rusty brown, sometimes almost 
black in the centre. The excrement (frass) adheres irregularly to its imder 
surface. Sometimes a portion of the under surface of the leaf opposite the 
mine also turns brown. When the eggs are laid in sets, the mines of the 
separate larvee usually become united, and even the mines of two sets may 
be united into one. One mine, fifteen millimeters long and ten millimeters 
broad, contained seven larvae, the scars arranged in two groups of four and 
three respectively. Another scar was near. As many as five mines, all in- 
habited, have been found on one leaf, and even eight mines made by ten 
larvae, though in this case some of the larvae had escaped. 
The Colour of Fishes . — A short paper (in French) was read at the British 
Association by M. Georges Pouchet on the mechanism of the changes of 
colour in fishes and Crustacea. The author referred to the fact that fishes 
often change in colour according to the colour of the objects by which they 
are surrounded : but he explained that this does not take place when the fish 
is deprived of the nerves that preside over the peculiar corpuscles to which 
the colour is due. The change does not take place in blind turbots ; and in 
the seeing turbot, if the nerves are divided which communicate between the 
eye and the skin, the change does not occur. If the fifth nerve is divided, 
the change takes place all over the body except the part to which that nerve 
is distributed. These experiments, M. Pouchet said, show that the change 
of colour is dependent upon impressions received by the nervous system 
through the organs of vision. 
