SOME KOTIFEEA FROM SPITSBERGEN. 309 



would be much more likely to be distributed by wind-storms or 

 by tbe agency of birds than would pool-dwelling species. 



The hypothesis that the present Eotifera fauna of Spitsbergen 

 has arisen from " accidental peopling " since the period of 

 maximum glaciation seems to me feasible enough, and I do not 

 seek any other solution of the problem of their presence, until 

 some proof is forthcoming that animals having some definite 

 relationship to Eotifera did exist there in stiU earlier ages. 



The present series of mosses, collected in the months of July 

 and August, 1921, had been in my hands for several weeks before 

 I was free early in January last to commence their examination. 

 I had scarcely started when I was forced to put on one side all 

 microscopic work, and it was not until nearly the end of March 

 that I was able to resume ; most of the gatherings were ex- 

 amined in April and May. Although the period of eight or nine 

 months between collection and examination was not excessive 

 from the point of view of the possibility of reviving a large 

 proportion of the Bdelloid Eotifera inhabiting the mosses, an 

 earlier examination would possibly have enabled me to revive 

 some few additional species. 



As the examination proceeded it was impressed on me that 

 either the larger species had greater endurance, or they had been 

 better able to protect themselves against the dangers common 

 to both large and small. I found that nearly every individual 

 seen of the larger species, such as Rotifer sordidus, Rotifer tardi- 

 gradus, Macrotrachela hahita and Mniohia russeola, revived after 

 a few hours' soaking of the moss, while a comparatively small 

 proportion of the specimens of the smaller species showed the 

 least trace of life. I think I am justified in stating also that 

 the Bdelloid Eotifera showed on the whole a greater power of 

 self-preservation than the eel-worms and water-bears associated 

 with them and subjected to the like conditions. 



Among the twenty-eight species found in these recent collec- 

 tions are two which have not hitherto come under my notice. 

 One of these is a practically spineless variety of the widely 

 distributed Bdelloid Pleuretra Brycei, a species whose type 

 form is remarkable for a very characteristic row of spines cross- 

 ing the back. Like most other spine-bearing species, it is 

 subject to almost infinite variation in the number and exact 



