CLATHRULINA GIKNKOWSKII. 63 



Mereschkowsky's description of the species differs 

 somewhat from that given above in so far as he 

 describes the surface of the capsule as studded with 

 short, blunt, spine-like projections arising from between 

 the apertures. As suggested by Penard, this is pro- 

 bably an error of observation due to the boss -like 

 appearance of the raised borders as seen in section 

 under the microscope, and Mereschkowsky's original 

 figures of the specimens he obtained from Lake 

 Onega differ but little from the figure. 



On the Continent of Europe Penard found this 

 species usually varying from 26 JJL to 33 /x in diameter, 

 rarely attaining 40 /x, and clearly differentiated from 

 C. elegans which he found to vary from 60 /x to 90 /JL, 

 but in N. America 40 /x in diameter is quite a usual 

 size for C. elegant (Leidy gives 30 /z to 44 //,) and 

 careful observation is necessary to distinguish between 

 the two species. 



Genus 11. HEDRIOCYSTIS Hertwig & Lesser. 



Hedriocystis HERTWIG & LESSER Arch. mikr. Anat. X, 1874, 

 Suppl. p. 225. 



Capsule or envelope pedicellate and pierced by 

 minute pores surrounded by facets or ridges giving it 

 a polyhedral form. 



Only two species have been recorded up to now 

 from Great Britain. H. peUucida Hertwig & Lesser 

 forms colonies, but the other two species have been 

 recorded only as solitary. 



SYNOPSIS OF BRITISH FRESHWATER SPECIES. 



Facets of capsule bordered by ridges. (1) H. reticulata. 

 Angles of capsule bearing spines. (2) H. spinifera. 



