ANIMAL NATURE OF DIATOME-ffi. 447 



in penicillate branches, which would seem to justify the 

 opinion of Kiitzing, who regards the Micromega penicil- 

 latum of Agardh as a variety of the same species, but 

 without noticing whether the Schizonema penicillatmn, 

 Chauvin, should also be placed there; but the same speci- 

 mens more denuded have no resemblance to Agardh's 

 figure. For this reason, before I consulted Kiitzing, 

 and before he published his work, I had given the name 

 of Micromega divaricatum to the one I had collected 

 very abundantly at Zava. 



Schizonema Blyttii, Ag., (Micromega.) 



The following species are ascribed by Kiitzing to the 

 preceding genus. 



Sckizonema minutum, Kiitz. 

 Schizonema humile, Kiitz. 

 Schizonema araneosum, Kiitz. 

 Schizonema coincides, Ag. 



I am indebted to the celebrated Berkeley for an oppor- 

 tunity of studying this species, and of convincing myself 

 of the existence of special tubes, which easily escape 

 observation, owing to their own tenuity and the size of 

 the Naviculas, whose uninterrupted series are narrowly 

 stipate. It is by these characters, and by the form and 

 proportion of the Naviculse themselves, that I was led to 

 the exact determination of the species, though the dimen- 

 sions are very different from those indicated by Kiitzing. 

 He says the Navicula? are as much as ^th of a line in 

 length, or 0'049 millim., (and he represents it, with a 

 power of 400 diameters, 8*9 millim., which would be about 

 half the size indicated,) and I, again, found it no more 

 than 0-024 in length, 0'005 in breadth of the secondary 

 (qu. primary ?) surfaces, and very variable in the always 

 broad secondary surfaces, which attain to 0'012 millim. 



