222 PROFESSOR LIONEL S. BEALE, P.K.C.P., F.R.S., ON 



and feathers, Avliicli, in their fully formed state, contain very 

 little moisture, wore all produced by moist livine; matter. 

 Every part of the dry feather of every adult bird, just 

 before each moulting period, was in the state of soft living 

 matter, consisting principally of water, and so with horn, 

 hair, nail and all other like structures in nature. But for the 

 f^oft structureless living particles, the production of these 

 tissues would have been impossible, so that, after all, the 

 whole process seems to be comparatively simple. Certain 

 materials are deposited in certain forms, and often in the 

 most beautiful patterns, in some extremely minute organisms, 

 nnd yet all these materials were at first dissolved in water 

 and then taken up by the living matter of the particular 

 living tissue, Avhatever it is destined to be, and arranged 

 in its previously determined ultimate form. Thousands of 

 diatoms can be identified and classed, according to the 

 predetermined arrangement of the silicious particles, which 

 is eftected by the liviiig matter of each class and species. 

 These hard tissues, the hardness of which depends on 

 organic or inorganic matter, exhibit Vvidely different 

 structures. The hair has a structure of its own ; but not only 

 no, but the hair of almost every hairy animal known, can be 

 distinguished and identified by its microscopical characters. 

 The external skin of insects, animal and vegetable hairs, 

 and all such tissues Avere formed by living matter rich ni 

 water. Though our teeth look like the hard matter of shell, 

 anyone seeing a thin section under the microscope would at 

 once discover the difference from shell, ivory, and other 

 structures. The difference of structure depends not on the 

 properties of the material of which in its fully formed state 

 it consists, but on the Poirer of the living matter by whicli 

 alone its formation was rendered possible. 



As I have remarked, a great many tissues are dry — Ave 

 may almost say, perfectly dry in their fully formed state. 

 Think of the Aving or the very hard coriaceous outer cover- 

 ing of the body and legs of a butterfly or a beetle. The 

 delicate muscles and far more delicate nerves Avithin the dry 

 outer sheath arc all moist, and so indeed are they in not 

 only in all classes of insects, but in all organisms. An 

 acting dry nerve or muscle, is a thing unknoAvn and impossible 

 in nature. 



It will be interesting, perhaps, if I may very l)riefly refer 

 to the great and most Avonderful changes which take place 

 in the formation of an insect. From the moist matter of 



