4 Transactions of the 



him for bis kind communications, and the courteous manner in 

 which he met my contradictions. 



Accordingly I have kept the two cork cells under occasional 

 observation, and though I have not been fortunate enough to meet 

 with another case of ecdysis, I do find that the cell which was 

 tenanted with the cheese-mite-looking acarus I have alluded to has 

 now numerous examples of Hypopus (or Acarellus) in it, and the 

 cell which contained Hypopi or Acarelli now contains many of the 

 suspected earlier stages. Of course there is the possibility of 

 migrations of the two creatures from their respective cells; but I 

 inchne to the view that the Acarelhne form is an adult one, gene- 

 rally parasitic on certain of the minute Arachnida, and in its early 

 stage or stages a vegetable feeder, and totally unlike the form it 

 ultimately assumes, being, moreover, in this early stage, fully 

 twice the size of the adult form. 



I doubt very much the suggestion both in Mr. Tatem's paper 

 and in the ' Micrographic Dictionary ' (under the authority of Dujar- 

 din), that the Hypopus or Acarellus is one of the early forms of 

 Gamasus ; for my cells are very much infested with these creatures. 

 To the best of my behef their young are white and very active. The 

 structure of the mouth also in my opinion indicates a wide difierence. 



The active little mites which I think are the larvae of the species 

 of Gramasus occurring in my cells, feed chiefly upon the same food 

 as the Podurse (crushed malt) ; but the adults will attack and 

 devour the young Podurae. I have also seen them seize and carry 

 off, after a struggle, the end joint of the antenna of a full-grown 

 one, — the antenna having been introduced into the hiding-place of 

 the Gamasus by its unsuspecting owner bent on exploration. In 

 the open space these Gamasi cannot cope with the superior strength 

 of the adult Podura, but when one of them dies from old age, the 

 Gamasi appear on the scene in force and soon clear away the corpse. 



On the other hand, the mite, which in my opinion is the larval 

 form of Hypopus, is very sluggish, and seems most at home when 

 absolutely immersed in filth, resulting from the decay of the excre- 

 ment of the Podurae, &c., and the fungoid growths arising in the 

 cells. I am sorry I cannot figure this creature, as I have never 

 been able to see it under a higher power than a two-thirds and 

 opaque illumination, except at the certain risk of the escape of all 

 the other inhabitants of the cell, and these have been so interesting 

 that I could not entertain the idea of disturbing them. The figures 

 I have given of the Hypopus Muscse are from life. I inverted the 

 cover of the selected cell on which I saw several of the Hypopi had 

 settled, and endeavoured by means of water and a fine camel-hair 

 brush to turn them on their backs. But though they might be 

 walking, immediately the brush touched them they clung to the 

 glass by means of the suckers at the posterior extremity so firmly, 



