Bibliographical Notices. 187 



The animal nature then of Diatomece is not proved by such spon- 

 taneous motion. 



As regards the so-called stomachs, I have before proved, that their 

 coloration by indigo is possibly a mere mechanical effect, and that 

 the assertion therefore that they are really stomachs is unauthorized, 

 and the more especially as these parts are so often wanting. 



As to the third point, the shell has indeed in many cases a great 

 similarity M^ith that of Mollusca in form, structure and marking, but 

 this is not constantly the case, and we find, in the higher families of 

 plants, cells, which in marking, form and other points present simi- 

 lar appearances. Witness the various forms of pollen, in which the 

 angles, spines, openings, &c. are not wanting. In this respect, then, 

 the approximation of Diatomece to different vegetable forms is as great 

 as to that of animals. 



On the other hand, the following points speak for their vegetable 

 nature : — 



1 . The great similarity of the compound forms to the Algae and 

 their origination by division. 



There are indeed also compound Infusoria, for example compound 

 monads and polypidoms ; but these are themselves questionable ani- 

 mals, and there is in them this great difference, that the individual 

 animal extends itself freely beyond its cell, while the Naviculse in 

 Encyonema, Schizonema and Micro?nega and similar genera grow in 

 the inner substance, and increase there as the cells of plants, and 

 vegetate only as cells. And the individuals in Fragilaria, Melosira, 

 Himantidium, &c. are as confined and unfit for the exhibition of ani- 

 mal motion. 



2. The internal soft organic parts, which I have indicated as go- 

 nimic substance, possess, as w^ell in their chemical comportment as 

 in their mode of development, peculiarities which are identical with 

 those of the contents of the cells in conferva- like Algae. 



This is especially shown in the genus Melosira and its allied ge- 

 nera, which not only in the form but also in the chemical properties 

 of their contents (through the presence of chlorophyll, which is in- 

 deed present in all Diatomece^ perfectly agree with Confervse. 



3. The formation of seed or fruit takes place similarly in different 

 Algae, never in true animals. 



4. The Diatomece, and especially the free motile NaviculcE, deve- 

 lope under the rays of the sun oxygen, like other decided plants. 



The evolution of oxygen is indeed remarked also in green monads 

 and Euglena, yet this proves nothing in favour of the animal nature 

 of Diatomece, but makes the real nature of those beings very doubtful, 

 and the more so as late observations show the origination of lower 

 vegetables from monads and Euglence. 



The weight of argument is we think certainly on the side of Dr. 

 Kiitzing, whatever may be thought of particular points, and the 

 whole seems to show, as Dr. Kiitzing had already distinctly stated 

 in a separate pamphlet, and as indeed was indicated in the ' Glean- 

 ings of British Algte * many years since, that there are beings in 

 which vegetable and animal life are so intimately combined, that 



