ZYGNEMA. 147 



This species is distinguished 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 MALFOKMATUM Hass. 



Plate XXX. Figs. 1, 2. 



Char. Filaments nearly equal in diameter to those of Z. CKS- 

 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, 

 which are considerably distorted for their accommodation. 



Zygnema malformatum Hassall, in Annals of Nat. Hist, 

 vol. x. p. 39. 



Hab. Cheshunt : 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 this 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 CATEN^FOKME Hass. 



Plate XXX. Figs. 3, 4. 



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

 Cells usually rather more than twice as long as broad. 

 Sporangia largely inflating the cells in which they are con- 

 tained, acutely oval. 



Z. catenceforme Hassall, in Ann. of Nat. Hist. vol. x. p. 39. 

 Hab. Cheshunt : A. H. H. Between Yapton and Wal- 

 berton near Arundel : Mr. Jenner. 



It is scarcely possible to distinguish the filaments of this 



L 2 



