ZYGNEMA. 147 



This species is clistinguislied from the former by the smaller 

 size of the filaments, greater length of the cells, and peculiar 

 zigzag disposition of the spiral thread ; it is not, however, a 

 very strongly marked species. 



15. Zygnema malpormatum Ilass. 



Plate XXX. Figs. 1, 2. 



Char. Filaments nearly equal in diameter to those of Z. a;s- 

 tivum. Cells about twice as long as broad, in each of 

 which a single spiral thread performs usually two revolu- 

 tions. Sporangia acutely oval, lying obliquely in the cells, 

 ivhich are considerably distorted for their accommodation. 



Zygnema malformatuni Hassall, In Annals of Nat. Hist. 

 vol. X. p. 39. 



Hah. Cheshimt : A. H. H. In a pond at Still Green, 

 and In the watercourse by the road side, near the Black - 

 boy's toll-gate : Mr. Jenner. 



I hesitated at first to regard tliis species as distinct from 

 Z. commune ; I now, however, entertain no doubt of the fact. 

 It is a very pretty species, and not uncommon. The form 

 of the cells is very distinct from that of Z. commune. 



16. Zygnema CATEXiEFORME Hass. 



Plate XXX. Figs. 3, 4. 



Char. Filaments a little finer than those of Z. mnlformatum. 

 Cells usually rather more than ticice as lo7ig as broad. 

 Sporangia largely iiflating the cells in which they are con- 

 tained, acutely oval. 



Z. catenaforme Hassall, in Ann. of Xat. Hist. vol. x. \). 39. 

 Ilab. "Cheshunt: A. H. H. Between Yapton and AVal- 

 berton near Arundel : il/r. Jenner. 



It Is scarcely possible to distinguish the filaments of this 

 r. 2 



