Naviculacca.'] infusouial animalcules. 307 



given by Schleiden, and is similar to the plan of making sections of 

 hair for the microscope : " This may be done by taking some of the 

 siliceous earth of Erbsdorff, and mixing it with mucilage, and, 

 before it is perfectly hardened, cutting off delicate plates with a 

 razor." (P. 18, f. 4) " exhibits a section of the upper part of a shield 

 prepared iu this way." (Principles Botany, page 594.) 



Kiitzing offers the following arrangement of the Nmiculmea, or, 

 as he calls them, Biatome(Z. He objects to the systems of other 

 naturalists, stating "that they have all one leading error : viz., that 

 of assuming as their basis characters extremely variable, and scarcely 

 to be employed in the identification of individual species, — such as 

 the presence or absence of a gelatinous indu\'ium, or of a stipes or 

 pedicle ; or the occurrence of the frustules solitary or concatenated." 



On the other hand, the structure of the shells being constant, he 

 has employed it in framing his an-angement, as follows : Tribe 1 . 

 Striated BiatomecB ; lorica siliceous, and either quite smooth or 

 transversely striated on the secondary side, but never vittate or 

 areolate (cellular.) Tribe 2. vittate (striemigej ; lorica siliceous (on 

 primary side) longitudinally (rarely transversely) vittate, smooth or 

 transversely striated, but never areolate. Tribe 3. Areolate (^Zellige) 

 Diatomea ; lorica siliceous, secondary side areolate or cellular. 



