DIATOMACE^E. 311 



that the eminently nitrogenous internal substance corres- 

 ponded with the generic substance, and that the oil 

 globules could take the place of starch. The multipli- 

 cation would be a simple cellular reduplication ; but it 

 would remain to be proved that it takes place, as in other 

 vegetable cells, either by the formation of two distinct 

 primitive utricles, or by the introflection or constriction of 

 the wall itself. Finally, there would still remain un- 

 explained the external motions and the internal changes ; 

 and we must prove the accumulated observations on the 

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

 argument than has hitherto been adopted, by those who 

 are opposed to this view. But again, admitting their 

 animal nature, much would remain to be investigated, 

 both in their organic structure and their vital f unctions ; 

 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, 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 Diatomacece 

 were proved by new and more circumstantial observa- 

 tions, 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." 



Did our space permit, many other arguments might be 

 adduced in favour of the views we have herein advocated; 

 we beg to refer the reader to the works of Kiitzing and 

 Ehrenberg for further information. 



Dr. Gregory believes that a large number of Diatomacece 

 usually divided into separate species, are nothing more 

 than transition forms of the same; and that more extended 

 observation proves that in form, shape, or outline, they 

 are not nearly so permanent in character as they were said 

 to be : he adds, " the more the Diatomacece are studied, the 



