MELOSEIRA. 397 



Derivation. From fjbsXos, a membej', and asipa, a chain. 



The species of the genus Meloseira admit of division into 

 two subgenera. Tlie first of tlicse, tlvc species of which are 

 chiefiy marine, and to designate which the word Sphcerophora * 

 might be employed, are cliaracterized by a pccuhar form and 

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

 and each contains, at first, one, and afterwards tAvo 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, tlie cells are truncate at their ex- 

 tremities, so that their articulating surfaces are directly applied 

 to each other, and slmjjly 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 Meloseii-a, amongst the Diatomacea;, seems to 

 have been constituted with a view of making apparent the 

 aflSnity which undoubtedly exists between the DiatomaceoB 

 and the AlgcB proper, not merely in form and developcment 

 approximating so closely to the genus Vesiciilifera amongst 

 the true ConfervcB, but also in a measure in its i-eproduction. 

 As in VesicuUfcra, 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- 

 rangium similar to that with which we are familiar in the 

 families ConjugatecR and Dcsmidccs. Notwithstanding this 

 striking resemblance to a genus of the Co7\ferv(B, the Melo^ 

 seircs are true members of the family of Diatomacea, as is 

 clearly indicated by their silicious natm-c, and consequent 

 striated structure. 



* Derivation. From ailutipcr, a globule, aiul (l>o(>uo, to bear. 



