MELOSEIKA. 397 



Derivation. From fisXos, a member ^ and asipa, a chain. 



The species of the genus Meloseira admit of division into 

 two subgenera. The first of these, the species of which are 

 chiefly marine, and to designate which the word Sphcerophora * 

 might be employed, are characterized by a peculiar form and 

 structure of the cells. The extremities of these are rounded, 

 and each contains, at first, one, and afterwards two spherical 

 vesicles or globules, divided by strongly marked double lines. 

 In consequence of there being no distinct articulating sur- 

 faces, the filaments are excessively fragile, so that it is rare 

 to find one of any length. 



In the second subgenus, with which we have chiefly to do, 

 and the species composing which are, for the most part, in- 

 habitants of freshwater, the cells are truncate at their ex- 

 tremities, so that their articulating surfaces are directly applied 

 to each other, and simply bilocular, and not globuliferous. 

 This subgenus admits also of further division, according as 

 the articulating surfaces of the cells are either plain or ser- 

 rated, and striated. 



The genus Meloseira, amongst the Diatomacece, seems to 

 have been constituted with a view of making apparent the 

 affinity which undoubtedly exists between the Diatomacece 

 and the AlgcB proper, not merely in form and developement 

 approximating so closely to the genus Vesiculifera amongst 

 the true ConfervcB, but also in a measure in its reproduction. 

 As in Vesiculifera, at a certain period, particular cells lose 

 their cylindrical form, and become globular or vesicular, and 

 contain endochrome : here, however, the analogy would ap- 

 pear to cease ; for this endochrome, so far as my observation 

 goes, never becomes condensed into a distinct organ or spo- 

 rano-ium similar to that with which we are familiar in the 

 families Conjugateos. and Desmidece. Notwithstanding this 

 striking resemblance to a genus of the Confervce, the Melo- 

 seirce are true members of the family of Diatomacece, as is 

 clearly indicated by their silicious nature, and consequent 

 striated structure. 



* Derivation. From (T<paipov, a glohule., and ^opew, to hear. 



