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ME. A. D. MICHAEL ON THE LIFE-HISTORIES 



posterior and a pointed anterior end ; was compressed dorso- 

 ventrallj, particularly at the posterior margin ; and had a more 

 or less plain sulcation round it, as thoagh dividing cephalothorax 

 from abdomen (in some specimens this was very marked). The 

 mass had the general form of a Hypopus, but there was not, in any 

 instance, any trace of legs, mouth, or other external organs. In 

 many instances the protoplasm appeared to be divided into large 

 cells, like an egg in an early stage of segmentation ; in others the 

 cell-division appeared to have gone further, the cells being much 

 smaller and finer, particularly in the posterior portion of the 

 creature, but some of the larger cells remaining; in others, pre- 

 sumably more advanced, the finer granulation was more uniform. 

 The mass was always motionless, but in one instance I did 

 find a living nymph within the case instead of the inert mass ; 

 this of course w^as ready to emerge. The cases from which the 

 occupant had emerged almost invariably contained the cast 

 cuticle of the protoplasmic mass, which cuticle did not show a 

 trace of l-egs, mouth, or any other organs. 



GrLYCIPHAGUS SPINIPES. 



At the end of 1885 I was at a farm-house for a short time, and 

 thought it a favourable opportunity to renew the investigation. 

 1 found in the chaff'-house, in the dust and chaff, and also attached 

 to the w^alls and beams, a number of cases which I at first 

 supposed to be similar to those I had before dealt with : I soon, 

 how^ever, found that these were even more opaque than the former 

 specimens, and that they were coarsely reticulated instead of 

 being finely vermiform in markings ; the empty cases also opened 

 differently, the posterior cuticle breaking away from the dorsal 

 and lateral, and remaining attached to the ventral, so that the 

 posterior end opened downward instead of upward, and w^as more 

 torn ; the hinder part of the dorsal cuticle also was usually split 

 along the median line and the two sides somewhat separated. It 

 was therefore probable either that they were in a different stage 

 from those observed in June and July of the same year, or that 

 they w^ere under different climatic or other conditions, or that 

 they belonged to a different species of Acarus. I finally found 

 that the last explanation was correct, and that these reticulated 

 eases were those of G. spinipes. Between the 28th December, 

 1885, and the 1st January, 1886, I found a considerable number 



