148 1). HRYCE ON THE ADINETAD^. 



the mouth, when feeding, particles not lying directly in the 

 path, and, when swimming, to propel the animal at a fair 

 speed. Such animals should, in moss-habitats, be able to 

 creep about and compete with Adineta for its food supplies, 

 and, perhaps, outstrip it there, as they and other free- 

 swimming forms have done in the open waters, and it is true 

 that in mosses which habitually grow in wet positions, such as 

 Sphagnum, many of such species do occur. Where, however, 

 the moss grows in a position usually dry, and is dependent for 

 moisture upon showers or falling dews, they are rarely met 

 with, and it is obvious that they cannot endure the alternations 

 of moisture and of dryness experienced by such dry-growing 

 mosses. 



Here, then, Adineta, in turn, has the advantage, for, with 

 many others of the Bdelloida, it can protect itself from the 

 effects of evaporation. When- the species was first described 

 by Mr. Davis in 1873, he stated, as the result of many trials, 

 that it possessed a surprising tenacity of life in this particular 

 direction, and it is on record that in this it excels even 

 Philodina roseola, another noted victim of artificial desiccation. 

 It is certain that the experiments by which Mr, Davis tested 

 the vitality and the endurance of this form were far more 

 severe than the conditions to which it would be subjected in 

 moss growing in the most exposed situations. 



It may be urged that the same advantages would be enjoyed 

 by Adineta oculata, a form remarkably close to A. vaga both in 

 structure and in manner of creeping and feeding, yet having 

 two eyes absent in the latter. I have found it but once, and 

 then on weeds from running water from the river Lea, and I 

 have seen it recorded by no other observer than its discoverer, 

 Mr. Milne, who got it from a pool near Aberdeen, or some 500 

 miles distant. 



There is thus some reason to believe that this eyed species is 

 rare, and I think we may infer that its scarcity in pools is (as 

 in the case of Adineta vaga, and so far as that scarcity may be 

 real) a result of its inability to swim. I made no experiments 

 with my colony, but the form may be supposed to have a 

 tenacity of life equal to that of vaga. Why has it not obtained 

 a like foothold in moss ? In his treatise descriptive of Callidina 

 symhintica (p. 49), Dr. Zelinka gives two reasons for his con* 

 elusion that that species leads a life of nocturnal activity and 



