MICROSCOPIC STUDY OF LOWEE ANIMALS. 53 



It has not been among tlie least important results of the new 

 turn which Zoological inquiry has thus taken, that a far higher 

 spirit has been introduced into the cultivation of this science, 

 than previously pervaded it. Formerly it was thought, both in 

 Zoology and in Botany, that Classification might be adequately 

 based on external characters alone ; and the scientific acquire- 

 ments of a JSTaturalist were estimated rather by the extent of his 

 acquaintance with these, than by any knowledge he might 

 possess of their internal organization. The great system of 

 Cuvier, it is true, professed to rest upon organization as its 

 basis ; but the acquaintance with this which was considered 

 requisite for the purpose, was very limited in its amount and 

 superficial in its character ; and no Naturalist formerly thought 

 of studying the history of Development as a necessary adjunct 

 to the Science of Classification. How essential a knowledge of 

 it has now become, however, if only as a basis for any truly 

 natural arrangement of Animals, must have become apparent 

 from the preceding sketch ; and it has thus come to be felt and 

 admitted amongst all truly philosophic Ifaturalists, that the com- 

 plete study of any particular group, even for the purposes of 

 classification, involves the acquirement of a knowledge, not only 

 of its intimate structure, but of its entire life-history. And thus 

 ITatural History and Physiology, — ^two departments of the great 

 Science of Life, which the Creator inextricably blended, but 

 which Man has foolishly striven to separate, — are now again 

 being brought into their original and essential harmony ; and it 

 is coming to be thought more credible, to give a complete eluci- 

 dation of the history of even a single species, than to describe 

 any number of new forms, about which nothing else is made out 

 save what shows itself on the surface. 



Thus every Microscopist, however limited may be his oppor- 

 tunities, has a wide range of observation presented to him in the 

 study of the lower forms of Animal life; with the strongest incite- 

 ment to persevering and well-directed inquiry, that the anticipation 

 of novelty, and the expectation of valuable results, can afford. For, 

 notwithstanding the large number of admirable records which 

 have been already published (chiefly, we must admit with regret, 

 by Continental !N"atUraIists) upon the developmental histoiy of 

 the lower tribes of Animals, there is no one of the subjects that 

 have been just passed in review, of which the knowledge liith- 

 eito gained can be regarded as more than a sample of that which 

 remains to be acquired. Records like those already referred to, 

 might easily be multiplied a hundred fold, with infinite advan- 

 tage to Science ; if those Microscopists who spend their time in 

 desultory observation, and in looking at some favorite objects 

 over and over again, would but concentrate their attention upon 

 some particular species or group, and work out its entire history 

 with patience and determination. And the observer himself 

 would find this ^reat advantage in so doing, — ^that an inquiry 



