THE CANADIAN FIELD-NATURALIST 



VOL. XXXV. 



GARDENVALE, QUE., Septtmbcr 1921 



No. G 



ON A NEW HELIOZOON FROM \'ANCOUVER ISLAND 

 By Chas. H. O'Donoghue, D.Sc, F.Z.S., 



Professor of Zoology, University of Manitoba. 

 (From the Biological Station, Nanaimo, B.C.) 



On tlie 25tli of May Mrs. Edith Berkeley 

 brought in some water, mud and debris 

 from a small pond near the top of a hill 

 above Hammond Bay Lagoon, about 420 

 feet above sea level. In this she noticed 

 a very large Heliozoon, wliicli she kindly 

 handed to me for examination. 



The pond is quite small and shallow, 

 surrounded by a close gi^owth of alders, 

 and is apparently pei-manent. It contains 

 a plentiful supply of several species of 

 Algae (Spirogyra, etc.), numerous fly 

 larvae, beetles and larvae, Copepods, Cla- 

 docera, and Hydra viridis and a number 

 of flagellate forms. 



The available literature has not yielded 

 a description of a similar form nor is there 

 anything like it in Wailes' excellent mono- 

 grapli number of tliis order (1) or Leidy's 

 account of the Freshwater Rhizopoda of 

 North America. As the present organism 

 is remarkable in several respects, it seems 

 worthy of putting on record. 



The animal is of very large size and ap- 

 pears to the naked eye as a bright green 

 sphere with a hyaline cover 2mm. in 

 diameter; indeed, it was so laige that it 

 was at first thought that it miglit be a 

 colony. Closer examination showed that 

 this was not the case and that it was a 

 solitary form, so that it is probably the 

 largest Heliozoon known, the only one ap- 

 proaching it being ActinospJiaerhnn 

 cicliliornii, which may attain a diametei- of 

 1mm. It belongs to tlie su])-order Clialaro- 

 thoraca in which the largest member is 

 probably Raphidiophrys viridis. wh'ich 



(1) The British Freshwater Rhizopoda and 

 Heliozoa, by J. Cash, G. H. Wailes and .1. IIop- 

 kinson, Vol. V, Heliozoa, by G. H. Wailes, Lon- 

 don. Ray Society, 1921. 



may rea(;h 90 micra or the colony 190 nricra 

 The present species is then approximately 

 22 times the diameter of the individual 

 or 10 times that of the colony. 



The body is spherical and measures 

 1.486mm. in diameter; it is enclosed in a 

 mucilaginous envelope .540mm. thick. Be- 

 yond this again the stiff pseudopodia ex- 

 tend 1.892mm. so that the total diameter 

 of the whole organism is 3.918mm. The 

 pseudopodia are quite numerous, reg- 

 ularly arranged and project to an equal 

 distance on all sides. They appear quite 

 stiff and w^ere not seen in active move- 

 ment. The mucous envelope was only 

 slightly granular and contained a few 

 tiny spherical algae and still fewer some- 

 what spindle-shaped ones. On the outside 

 of it were sparsely scattered tiny curved 

 spicules apparently siliceous and some- 

 what pointed at each end. The envelope 

 ran up a short distance on each pseudo- 

 podium. 



pjg. 1.— RAPHIDIOPHRYS MAGNA, general 

 view. The darker area situated slightly excen- 

 trically represents the nucleus and cndoplasm. 

 A. — A small portion of the symbiotic Algae 

 to show their characteristic dendritic arrange- 

 ment. 



