Desmidiei^.J infusorial animalcules. 235 



generally. He says, " Arthrodesnms possesses a small colourless 

 corpuscle on the wall of the cell, which looks like a nucleolus. 

 Etiastnim frequently exhibits, among the green contents, two 

 obscure bodies resembling nuclei, always one in each half, when the 

 division tlu'ough the middle takes place. These are not attached to 

 the cell-membrane, but lie fii'ee in the midst of the cavity ; they 

 appear to possess a dark centre (nucleolus ?) and a clear periphery 

 (enveloping-layer ?).... In Closterium, a nucleus lies in the centre, 

 which possesses a tliick whitish nucleolus within a clear enveloping 

 layer. It is coloured bro^\Ti by iodine, and wholly resembles the 

 nucleus in Spirogyra.'" Elircnbcrg, who previously noticed these 

 nuclei considers them analogous to fecimdating glands. Both na- 

 turalists agree as to their probable function, but each gives an 

 explanation as they view them, either as plants or as animals. 



Eespecting the nature of the Desmidiem, Mr. Ealfs affirms that 

 they have as strong a claim as the Conjugates or PalmellcB can have, 

 to rank with the Algse. On the other hand, he considers the proper 

 station of the DiatomactB very doubtful. 



Ehrenberg's reasons for placing the Desmidiea in the animal king- 

 dom are the following : — That they exert a voluntary motion ; that 

 they increase by transverse self- division ; and that the Closteria have 

 at their extremities apertures, and protruding organs, continually in 

 motion. Although two of these reasons apply only to the genus 

 Closterium, Mr. Ealfs will admit that if the Closteria can be proved 

 animals, the questions as to the other genera will be decided. As to 

 the possession of voluntary motion, he protests against the use of the 

 word voluntary as prejudging the question. That the Desmidiem 

 move, must be admitted ; but, whilst making this admission, he 

 maintains that in the lower tribes of organic Hfe, motion is not an 

 indubitable sign of an animal nature. Indeed, Mr. Ealfs and Mr. 

 Jenner, have both failed to perceive any actual movement : (see 

 Closterina p. 179), and whatever may be the motive power of the 

 DesmidiecB, according to those observers, they possess it only in 

 common with acknowledged Algae, and in a less degree than either 

 the DiatomecB, the Oscillatoria, the sporules of various AlgEe, or 

 indeed their own sporules. Ehrenberg considers, that increase by 

 voluntary division, is the character which separates animals fiom 



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