Destnidiecs.} infusorial animalcules. 291 



ScENEDESMUS duplcx. — Cclls slciulci', fusiform, sigmoid, tapering at 

 each end into a fine point ; after division, closely connected for 

 about half their length. 



S. antemiatus. — Cells fusiform, somewhat ventricose at the middle; 

 ends cuspidate, each terminated by a minute orbicular globule. 



The description of these genera, and some others since estabhshed 

 by Ehrenberg, as also that author's characters of Odontella, wiU con- 

 clude this section. 



Genus Sphaerasteitm. The round star Animalcules are characterized 

 by theii" members being free, having a simple univalved smooth and 

 turgid lorica, and by forming, during self- division, different shaped 

 groups. A slight change of place or locomotion has been observed, 

 but little or nothing of their organization is knoAvn, though Bory and 

 Turpin have stated the existence of male seminal glands in S. 

 quadrij\(ga. 



S. pidum has oval green corpuscles, passing into spherical clusters, 

 of the form of a mulberry. Size of berry l-480tli; of single 

 member l-1920th. Found with Micrasterias. 



S. qiiadrijugum has oblong green corpuscles, four being united into 

 cubical mass, perforated at the middle. Size of berry l-570th; of 

 single member 1-1 200th. Found with the former species. 



Genus Microtheca. The spinous disc Animalcules. It contains only 

 one species, and is characterized by being free, and possessing a 

 simple square compressed lorica, composed of one piece. In its 

 organization it approaches that of GaUio?iella and Achnanthes. 



This genus is a very doubtful member of the Besmidiece. It 

 presents no indication of the characteristic division into two valves ; 

 and the golden colour of its only species, is a character of Diaiomece, 

 and, consequently, an argtiment against its being one of the 

 Desmidiece. 



M. octoceros has a square transparent lorica, with spines, 

 (P. 2, f. 119, 120, the first a front, the latter a side view.) It is of a 

 golden colom-, variegated ; change of place has not been observed. 

 " I received," says Ehi-enberg, "in September, 1832, phosphores- 

 cent sea-water, from the harbour of Kiel. On the 23rd of October 

 I found therein this yeUow creature, which appeared very similar to 



