226 DESCRIPTION OF [^Poli/gastnca. 



though the conjugation simi^ly is analogous, yet the produced (spo- 

 rangia have no proper characteristics, as they resemble the fronds 

 producing them, save in their larger dimensions. This variation, 

 M. Thuret contends, renders the phenomena of conjugation inde- 

 cisive of the vegetable character of the Diatomea, " for it is clearly 

 not here a mode of reproduction, — it is only a second mode of multi- 

 plication of fiiisttJes, veiy cmious, and very abnormal." 



But a still more decisive objection to considering conjugation a 

 proof of vegetable organization, is to be found in the recent disco- 

 very of Siebold, that that process is met T\dth in the animal Idngdom, 

 and that he has witnessed it in Diplozoon paradoxum, and in Actino- 

 fhrys Sol : the former an JEnfozoon, previously regarded as a single 

 animal, but in fact a conjugated state of a Parasite, known as the 

 Diporpa ; the latter one of the Infusoria. 



A tliii'd objection to the argument that conjugation is favoiu'able to 

 these organisms being Algce, is that the higher kinds of AlgcR do 

 not conjugate. It would therefore follow if we consider them as AlgcB, 

 that the lower tribes of these plants require a renewal of the siDennatic 

 force, while the higher ones do not, which would be contrary to all 

 our ideas of physiological laws. 



The notion in'opounded by Ehrenberg, that the granules in the 

 interior of Bacillaria — including the Chsterina, are ova, has not met 

 with support from the observations of other naturalists. In Clos- 

 terium a circulation of the granidar contents, involving also many 

 of the stomach sacs of Ehrenberg, has been witnessed by most 

 microscopists : and in one of the Biatomece, supposed to be a species 

 of Navicula, Niigeli says, " I observed a pretty rapid cu'culation of 

 the granular contents, the granules passing jfrom the nucleus out- 

 wards along the edges, and back again to the former." (Ray Society, 

 1845. p. 221.) 



The occurrence of this phenomena is adverse to the opinions of 

 the internal animal organization, supposed by Ehrenberg ; whilst it 

 at the same time favours the hyi)othesis of the vegetable nature of 

 these organisms, the circulation being similar to that so common in 

 vegetable ceUs, and the cii'culating gTanules and vesicles, resembling 

 those of various confervas, and minute Alcjm. (See Introduction to 

 Desmidiacea and Naviculacea.J 



