DEVELOPMENT AND IMMATURE STAGES. 169 



thine wrinkling shown at PL VIII, fig. 16. The con- 

 tents of each case were more drawn to the anterior end 

 than is usual in the nymph before ecdysis. The first 

 step was to ascertain that they were not simply dead 

 creatures. Towards the end of May I placed three in 

 one of my small glass breeding-cells, making the con- 

 ditions as favourable as I could; on June 10th 

 three immature G. domes ticus emerged from the cases ; 

 which did not split irregularly like ordinary nymphal 

 skins, but usually opened by the posterior end of the 

 case, which had been concave, being pushed out so as 

 to become convex ; and separating from the lateral and 

 ventral parts of the case but remaining attached to the 

 dorsal (PI. VIII, fig. 14). The cases, although open, 

 were not entirely empty; I found that each contained a 

 cast skin. After some unsuccessful attempts I again 

 isolated several cases in a cell on July 30th, 1885 ; in a 

 week two nymphs had emerged, more subsequently 

 followed. I placed three of these nymphs in a separate 

 cell ; in about a week they became inert ; a few days 

 later an adult ? emerged from the cuticle of one, the 

 others soon followed. The cast skin from which the 

 adult emerged was thin and fine ; very different from 

 that of the cases. It was thus ascertained that the 

 cases were a penultimate-nymphal stage, i. e. the nymph 

 which emerged from the case became adult at the first 

 ecdysis. 



I was unable to resume the enquiry until January, 

 1888 ; on the 25th of that month 1 placed four cases in 

 a cell, but in spite of the best conditions I could give 

 them, they did not emerge until July 15th. On April 

 9th I placed a number of cases in three separate cells ; 

 on April 21st I found an inert nymph of G. domes ticus, 

 which had emerged from a case and become inert. I 

 had not examined the cell for two days. On April 

 26th the adult emerged, and a second nymph had 

 emerged and become inert; on May 1st the adult 

 emerged from this. 



I dissected a large number of the full cases ; in each 



