D. BRYCE ON THE ADINETADj:. 149 



diurnal rest: — the first is, that, wet weather excepted, the 

 mosses in which it lives are at their maximum of dampness 

 during the night as a result of dewfall, and the second, that 

 that species has no eyes. Mr. Percy Thompson has also 

 suggested, apropos of some other forms, that a species with 

 eyes, becoming resident in moss, would possibly tend to 

 become a blind form. These three principles, dovetailing into 

 each other as they do, may well account for the absence of 

 Adineta oculata from moss- washings. It is sufficiently near to 

 A. vaga to suggest that both forms were originally one and the 

 same, that with eyes being possibly the older type, and that 

 the eyes were lost in A. vaga, either by its having become a 

 feeder by night, that season being the most favourable in the 

 dry-growing mosses, or because, when living among the wet 

 mosses, it would be in the dark, even while able to be active in 

 hours of daylight. 



Returning again to A. taga, I have for some little time 

 thought that there exist two well-marked varieties of the 

 species. I do not say that intermediate forms do not occur, 

 but the majority of individuals belong definitely to the one 

 variety or to the other, and both are frequently present in the 

 same moss. That which I call the var. major is usually 

 larger and stouter, with the head broader in. proportion, the 

 styles, which protrude just above and to right and left of the 

 anterior edge of the prone face, strong and bold, while the 

 posterior trunk segments are sharply divided from each other. 

 The var. minor is altogether slighter, the styles are incon- 

 spicuous, while the trunk segments decrease gradually and 

 without break of lateral outline. It occurs much more 

 frequently than the other. I do not know that these points of 

 divergence are so important as to mark the forms as distinct, 

 species, but I hope, by breeding them apart, to ascertain whether 

 they are actual races or merely stages of development. 



What I term styles are apparently modifications of the 

 membranous flaps, conspicuous in many of the Callidinse at 

 the tips of the column. They have hitherto been described as 

 hooks, but I think erroneously. 



I conjecture that these two forms were known to Mr. Milne, 

 who, writing in 1886, was seemingly unaware that a descrip- 

 tion of A. vaga had been published long before, for, while 

 stating that he had found two other species with coronas and 



