DEVELOPMENT AND IMMATURE STAGES. 159 



I now again tried the converse experiment ; I 

 collected Tyroglyphi, and placed them in two kinds of 

 cells : (1) small cells consisting of a glass ring (section 

 of tube) cemented on to an ordinary microscopical 

 slide, the upper edge of the ring being ground smooth, 

 so that the cover, which is another microscopical slide, 

 would lie quite closely on it, being held on by a tie or 

 clip ; in each of these I put only one or two specimens, 

 so that I could watch and know each individual. (2) 

 Larger similar cells (small dissecting troughs), the 

 cover pierced by a few small holes closed with fine 

 muslin, and so placed that they can be made to let air 

 into the cells or not, as desired, by moving the cover ; 

 in these cells a number of specimens can be placed if 

 desired. I now tried two of these larger cells, each 

 with a considerable number of Tyrogiyphi, and when 

 they were breeding freely allowed one cell to get dry, 

 keeping the other in proper hygrometric condition. 

 I did not find that I got more Hypopi in the cell that 

 dried than in the other. On the contrary, I got more 

 Hypopi where breeding was under favourable circum- 

 stances, and consequently young nymphs more abun- 

 dant, but I did find that as the cell dried the Tyro- 

 giyphi retired into any hole which afforded moisture. 

 I kept a small piece of blotting-paper in the cell to 

 damp when requisite; as the cell dried the Tyrogiyphi 

 usually got under the blotting-paper ; if fresh moisture 

 were added they came out again, if not they died, and 

 were not seen again. The Hypopi endured drought 

 much better, but if it were too prolonged they died 

 also. I repeated this experiment several times, but 

 always with the same result. This may account for 

 the manner in which Megnin's Tyrogiyphi disappeared 

 when his cage got dry, and reappeared when fresh 

 moist fungus was added. 



At this time, April, 1882, I took two similar Hypopi 

 from moss in the neighbourhood, where they were 

 numerous, and placed them alone in one of the smaller 

 cells on blotting-paper. In a few days they became 



