DEVELOPMENT AND IHMATTJKE STAGES. 171 



about (Hypopi are usually active). It was evidently 

 not fitted for existence as a free creature, but was 

 undoubtedly alive and fully formed (PI. VIII, fig. 17). 

 Most of the Hypopi dissected out were incapable of 

 motion ; only a few were able to move their legs. I 

 searched the chaff dust, walls, and beams of the chaff- 

 house many times in hopes of finding active Hypopi, 

 but never succeeded in doing so. I found one or two 

 inactive, which seemed as if from some accident the 

 cases had been broken from them. On January 2nd, 

 1886, I took one of these and one dissected out of a 

 case, and put them in a separate cell ; on January 15th 

 one emerged, leaving the cast hypopial skin behind; 

 the creature that emerged was a nymph of G. spinipes. 

 On January 16th I dissected four more Hypopi out of 

 cases and put them in another cell; three eventually 

 died, but one remained unchanged for nearly four 

 months ; I watched it every day, and on May 24th it 

 underwent ecdysis and a healthy nymph of G. spinipes 

 emerged. While this experiment was progressing I 

 also watched the cell in which I had placed the cases. 

 One nymph only had appeared, but on May 26th two 

 more cases were open and two Hypopi had apparently 

 crawled out of them ; when touched they appeared 

 inert and incapable of motion, but a few days after 

 nymphs of G. spinipes emerged from them. 



In January, 1888, I resumed the enquiry. I put 

 seven full cases in a separate cell : I could see the 

 Hypopus moving its legs in one ; on February 7th one 

 nymph emerged, on February 8th a second; I put 

 tkese in a fresh cell. On February 9th the first of 

 these became adult ; on February 26th the other. I 

 tried numerous other cells with confirmatory results. 



I came to the following conclusions : 



1. There is a Hypopial stage in the life-history of 

 Glycyphagus., but in the species experimented on it is 

 far less developed than in Tyrocjlyplms, and is not an 

 active stage. 



2. That we did not know whether it occurs in all 



