396 



fications of tubes or cells. But towards the bottom of 

 the scale of organized beings we find, both in plants and 

 animals, the greatest simplicity of structure, and in each 

 kingdom, many w^hich consist only of an aggregation of 

 cells. A large proportion of cryptogamic plants have this 

 simple structure ; and amongst animals may be mentioned the 

 different species of Diatoma, Fragillaria, &C.5 which, from 

 the similarity of their structure, are not unfrequently classed 

 amongst the vegetable Confervse, but which, in respect of 

 their remarkable powers of locomotion, seem to claim the 

 rank of animals. Certain species of Entozoa have an equally 

 simple structure ; the same is true with regard to the Cynthia 

 mammillaris, mentioned above. In the mode of their first 

 development, as observed by Schleiden, and, subsequently, 

 by many other microscopical physiologists, all the tissues, 

 both of plants and animals, are strikingly similar. Dr. 

 Lindley considers the presence of starch granules in the 

 tissues of plants to be the most unexceptionable mark of 

 their vegetable nature ; but it is, perhaps, doubtful whether 

 starch is developed in all beings whose vegetable nature is 

 fully acknowledged. 



Animals differ markedly from plants in some of their 

 functions. The functions of vegetables are those of nutri- 

 tion and reproduction, called the organic, or vital functions ; 

 animals possess, in addition to these, those of relation, viz., 

 sensation and motion. This is what Linnseus made the 

 ground of distinction in his brief statement, " Lapides 

 crescunt, vegetabilia crescunt et vivunt, animalia crescunt^ 

 vivunt et sentiunty 



5. These animal functions of relation are performed 

 through the agency of a nervous system, in the possession 

 of which, likewise, animals differ from plants. No nervous 

 system has ever been demonstrated in a plant ; some fanci- 

 ful botanists, as Braschet, have thought that they discovered 



