n.'EMATOCOCCUS. 321 



ner the frond again obtains a diaphanous margin, but different 

 from that with which in the beginning it was surrounded." — 

 Mencgh. 



49. H^MATOCOCCUS Ag. 



Char. Cells spherical or oval, of various sizes, each invested 

 with one or more concentric vesicles or membranes, mul- 

 tiplied either by division or by granules formed within the 

 parent cells. 

 Derivation. From aljia, blood, and kokko?, a berry. 



Agardh has evidently included in his genus Hccmatococcus 

 productions gcnerically distinct; as, for example, //. sanguineus 

 and H(Bm. or projjerly Protococcus nivalis : he therefore would 

 appear not to have entertained any precise ideas in reference 

 to his genus beyond the fact of the contents of the cells of 

 some of the species being of a red colour. Meneghini in the 

 memoir so often referred to, limits the genus Hcumatococcus 

 to one species, the H. nivalis of Agardh, a production which 

 assuredly does not differ even specifically from the Proto- 

 coccus nivalis of the same author, and constitutes a ncAV genus 

 Microcystis for the reception of //. sanguineris and its allies, 

 the adoption of which, as //. yiivalis Ag. cannot be allowed 

 to remain in that genus, is rendered unnecessary. 



Of the two terms Ha^matococcus and Microcystis, the latter 

 is by far the more applicable, the former being in some de- 

 gree objectionable, inasmuch as it is founded on the colour of 

 the globules, a colour confined to a limited number of the 

 species of the genus. ISIeneghini thus defines his genus 

 Microcystis : — 



" Frond mucous ; in the beginning definite, at a later period 

 effused, including globules clothed in vesicles and multi- 

 plied by a quaternary division or by gramdcs evolved 

 within, constituting so many new fronds." 



" Each globule, in the same way as those of the Pleurococci, 

 shrinks from its involucre, and then appears to be clothed 

 with its proper vesicle. A process of this kind is frequently 



Y 



