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XIII. 



THE EVIDENCE FROM THE CONSTITUTION OF 

 COLONIAL OR COMPOUND ANIMALS. 



AMONGST the many aspects in which the biologist is accustomed 

 to view the universe of life, few possess a greater interest than that 

 which deals with the nature of animal and plant personality, and 

 with the structural philosophy of the living frame. It is not suffi- 

 cient for the due investigation of living structures that the forms of 

 animals and plants be compared, and their more obvious differences 

 and peculiarities noted and recorded in scientific annals. Such details 

 and such procedure suffice perfectly for the ordinary run and course 

 of biological work, and form, no doubt, the source of the every-day 

 knowledge on which natural-history science grows and progresses. 

 But a higher era of scientific thought intervenes when philosophy, 

 in its search after relationships and causes, steps forward to correlate 

 and utilise the knowledge observation has acquired. The higher 

 questions of cause and origin are not solved by observation alone. 

 It requires and demands the power of placing facts in appropriate 

 light and shade ere the mutual relations of these facts can be deter- 

 mined, and before their place in the sy sterna natures can be definitely 

 ascertained. Judged by this criterion and standard, there are some 

 topics of biology which altogether belong to the region of the abstract 

 and the transcendental. Patient industry may discover, for instance, 

 that a crayfish within the egg repeats, as a stage in its development, 

 the likeness of a form represented to-day by the adult state of some 

 lower crustacean ; but it requires philosophy of a transcendental 

 kind to see what that fact means, and what such a discovery implies 

 to the universe of life around. One may perfectly appreciate by 

 ordinary observation that a horse walks on the single toe of each 

 foot, and that its two " splint-bones " represent useless rudiments of 

 other two toes; but it is through an exercise of abstract science 

 alone that we can form the concept of a single-toed horse having 

 arisen from a three-toed one ; and from the latter phase of develop- 

 ment extend a like thought to that of other living beings. The 

 applications of philosophy to the facts of nature remind one strongly 

 of the most singular and mysterious work of that nature in the pro- 

 duction of the living thing itself. In the performance of that function, 

 we require a certain quantity of the substance called " formative 



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