On the Use of the Microscope as an Aid to the 

 Classification of Animals. 



By B. T. Lowne, M.R.C.S. Eng. 



(Read October 22nd, 1869.; 



There are several ways in which the microscoiDe has afforded im- 

 portant aid to us in studying the relations of the various classes 

 and species of animals to each other. Its uses in discriminating the 

 affinities of the minuter forms of life, and in examining minute 

 organs, are too obvious to need enlarging upon. Again, the facts 

 brought to light by means of the microscope, especially during the 

 past few years, in the embryology and development of animals, 

 have been of the utmost importance. 



It is not, however, to such classes of facts as the above that I 

 intend to draw your attention to-night, but to a hitherto unworked 

 field of enquiry. 



I believe histological structure, that is, the form and structure 

 of the ultimate elements of the bodies of animals, is destined to 

 afford an important clue to their relations to each other, and will 

 perhaps, when clos,ely studied, go far to settle the great zoological 

 question of the day — how far animals and plants are related to each 

 other by descent. 



Perhaps it is almost premature for me to speak of this sub- 

 ject to-night, but its issue is so important, and the facts I have to 

 bring before you are so suggestive, that I cannot refrain from say- 

 ing a few words upon it. 



On a prima facie view, the histological structures of all animals 

 appear to be identical ; for instance, the epithelial cells of molluscs, 

 insects, and vertebrates present the same essential characters. I do 

 not know of any means by which the conical epithelium of the 

 stomach of an insect could be distinguished from that of a man, 

 nor do I know any mode by which gland cells, pigment cells, or 

 muscular fibres belonging to one class of animals, could be distin- 

 guished from those of another class. 



It is by means of this close resemblance of tissue that 

 we are mainly enabled to judge of the functions and characters of the 



