418 



THE MICROSCOPE. 



exterior organs of motion to be false, by a clearer line of 

 argument than has hitherto been adopted by those who 

 aro opposed to this view. But again, admitting their 

 animal nature, much would remain to be investigated, 

 both in their organic structure and their vital functions ; 

 excepting this, so far as we know, we have only one diffi- 

 culty to overcome, that of the probably ternary non- 

 azotised composition of the external gelatinous substance 

 of the peduncles and investing tubes. But as the presence- 

 of nitrogen is not a positive character of animal nature, 



9 ; 



Fig. 220. 



1, Cymbella Ehrenbergii. 2, Side view of The same, showing an arrangement of 

 the sarcode and pseudopodia. 3, Pleurosigmata lanceolatum. 4, Lateral view 

 of a portion of the same. 5, 6, and 7, Pinnularia. 8, Diatoma vulgare. 9, 

 Nitzscliia varvula. 



so the absence of it is not a proof of vegetable. And, in 

 order that the objection should really have some weight, 

 it would be well to demonstrate that this substance is 

 isomeric with starch. For then, supposing all the argu- 

 ments in favour of the animal nature of Diatomaceas were 

 proved by new and more circumstantial observations, this 

 peculiarity, if it deserve the name of objection, might still 

 be regarded as an important discovery. We should then 

 have in the animal, as well as in the vegetable kingdom, a 

 ternary substance similar to that forming the bases of the 

 vegetable tissue." 



