454 ANIMAL NATURE OF DIATOME^E. 



(Schizonema, Sp. nov. Zan. in lit.) 



Zanardini found it plentifully in the Lagunes of Venice. 

 Form : globular tufts, of three or four centimetres in 

 diameter, which, dried upon paper, form an uniform spot, 

 in which, by a lens only, the separate threads can be 

 distinguished. Though Kiitzing assured me that this 

 was a new species, yet by its mode of ramification it 

 resembles S.flagelliferum. 



This long speciological discussion may to some appear 

 misplaced, or at least at variance with the proposed plan 

 of this essay, intended as an organographical and physio- 

 logical examination of the genera. The principal ground 

 of my defence is the- great importance of Kiitzing's most 

 valuable work, and the respect that is due to so great an 

 author. Who would dare to subject so immense a 

 collection of most delicate observations to critical exami- 

 nation, unless he were able to counterpoise them with a 

 series of his own observations, if not equally numerous, 

 at least sufficient to prove the critic in possession of 

 means and practice, and diligence and honesty of ob- 

 servation ? Such has been my object, and if I have erred 

 in any respect, for I must admit that it is easy to err in 

 such minute researches, I hope, notwithstanding, to have 

 demonstrated both the excellence of the instrument 

 expressly made for me by Amici, of which I am sure 

 that no one possesses its equal, Mohl only excepted, and 

 the good intentions by which I endeavour to prove my 

 gratitude to the most gracious Prince who bestowed 

 upon me so munificent a gift. I believe, too, that an 

 examination of various specific forms is necessary, that 

 we may deduce from them some considerations as to the 

 organology of the genus. 



The presence of minute Naviculse among the larger, to 



