430 THE DISEASES AND DISORDERS OF THE OX. 



spending manner. The reproduction in the mimickers of the 

 most minute lines, of the particular kind of flight, of the mode of 

 resting, are also to be perceived, while the fact that even varieties 

 are copied, shows us to what extent this protective acquisition 

 has been carried. It is matter of common observation that pro- 

 tective coverings are largely developed in numerous animals 

 «uch, for instance, as tortoises, crabs and lobsters, the Hippo- 

 campidse, or sea-horses, the amphisile, while the curculionidee 

 among beetles, exemplify the possession of a highly perfected 

 defensive armour. The term ** mimicry " was introduced to 

 express superficial likenesses among animals which difi'er greatly 

 in regard to intimate structure from those imitated, and the 

 subject has been elucidated by the able researches of Wallace, 

 Bates, Trimen, and others. Protective mimicry is only explic- 

 able on the theory of evolution, and the phenomena which are 

 to be classed under this helad afford some of the best arguments 

 which can be adduced in favour of this induction. Of all 

 biological subjects, one of the most interesting is the study of 

 those extraordinary disguises which the exigencies of existence 

 seem to have forced upon some animals. The investigation of 

 such peculiarities is of still greater value, since we now look 

 upon life not as one vast drama in which each animal and plant 

 plays a subsidiary, purely temporary, and comparatively fixed 

 part, but rather as a vast moving panorama, so to say, of which 

 the concluding scenes, connected with the first as they are by 

 laws of causation,^ are made ever the more perfect. Finally, 

 what practical lesson can be derived from the study of protective 

 expedients, as shown in the members of the animal kingdom ? 

 Paying due regard to the fact that such resources are most 

 especially apparent in the lower forms of life, may we not justly 

 infer that although protectionist measures may from time to 

 time facilitate the maintenance and well-being of any given 

 individual or group of individuals, still they do not, and pro- 

 bably never can, afford more than a transient succour, and 

 that they are only apparently and temporarily helpful in the case 

 of an aggregate which would otherwise be weak and retrogressive, 

 if not effete. 



In studying the strange phenomena of parasitism, one cannot 

 but be struck by the extraordinary fact that the highest animals 

 are oftentimes destroyed by the lowest, being completely at their 



