Mr. HassalPs Notices of British Freshwater Conferva. 39 



This species is to be distinguished from Zygnema commune 

 by its longer and ventricose cells, and by the presence of the 

 curved lines at the joints, which are however met with in 

 other species besides this. 



In a small lake belonging to Mr. Bridgman near Cheshunt, 

 and at other places. 



Zygnema aequale. Filaments of less diameter than those of 

 Zygnema subventricosum ; cells usually eight times as long 

 as broad, containing about six turns of a single spiral tube ; 

 spores oval, contained within the cells, the inflation of which 

 they never occasion. 



I have given this species, which cannot be confounded 

 with any of the others described in this paper, the specific de- 

 nomination of cequale, on account of the evenness of the fila- 

 ments, which when they contain the spores never exhibit the 

 smallest trace of inflation, and the uniform length of the con- 

 necting tubes. 



Neighbourhood of Cheshunt. 



Zygnema commune. Cells about three times as long as broad, 

 in the interior of each of which a single spiral tube per- 

 forms about two and a half revolutions ; spores not produ- 

 cing any inflation of the cells in which they are placed. 

 This species has occurred to me in the neighbourhood of 



Cheshunt, and in ponds at the back of the Norland estate, 



Notting Hill. 



Zygnema catenceforme. Cells rather more than twice as long 

 as broad, each containing about two revolutions of a single 

 spiral tube ; spores largely inflating the cells in which they 

 are contained. 



It is scarcely possible to distinguish the filaments of this 

 species from those of Z. commune before conjugation : after 

 this has occurred, the difference in the length of the cells and 

 the form of these is so obvious as to leave but little doubt of 

 its being distinct from that species. If a condition of any, 

 however, it is of Z. commune. 



Mr. Bridgman's pond, Cheshunt. 



Zygnema malformatum. Cells about twice as long, in each of 

 which a single spiral tube performs usually two revolu- 

 tions : spores lying obliquely in the cells, which are a good 

 deal distorted for their accommodation. 

 I should hesitate to regard this as distinct from Z. commune, 

 but that it has occurred to me in considerable abundance, un- 

 mixed with any filaments which I could decidedly refer to 

 that species. 

 Cheshunt. 



