U^VJ YOFJC 



THE 



MONTHLY MICROSCOPICAL JOURNAL. 



JANUAKY 1, 1874. 



I. — Notes on so-called Acarellus. By S. J. McIntike, F.K.M.S. 



{Bead lefore the Royal Microscopical Society, Nov. 5, 1873.) 

 Plate XLV. 



Whilst watching the habits of Podurae and Pseudo-scorpions I 

 have often been conscious of the presence in the cork cells of unin- 

 vited guests in the shape of acari of various species, either collected 

 unintentionally by the camel-hair brush into the test tube together 

 with the desired captures, or migrating from one cork cell to 

 another of their own free will and pleasure. One of these has 

 engaged a good deal of my attention. 



The first time I noticed it was in its character as a parasite 

 upon a rather fine specimen of Obisium ; six or seven of them 

 clinging firmly to the legs and cephalothorax of the host, and 

 remaining in the position they had taken up for days without 

 causing any apparent inconvenience to the obisium. Indeed, at 

 first I scarcely recognized them as parasites. Afterwards it was 

 by no means uncommon in the locality which was my happy hunt- 

 ing ground (a back-yard with an apology for a garden at the rear 

 of oui" house) to find under old bits of wood, brickbats, &:q., Gamasi 

 and Obisia, infested with these parasites, and once I caught a 

 Gamasus with a perfect load of thirty or so of them on its back 

 and legs, rendering it quite unrecognizable at first sight. By this 

 time I had come to the conclusion that the earth in this particular 

 place swarmed with this acarus, and it was no longer a novelty. 

 I felt quite certain, moreover, that there were two species. 



On transferring the infested Obisia, &c., to my cells, I soon 

 found that their httle parasites occasionally left the host's back and 

 wandered over the floor and sides of the cork cells ; sometimes 

 fixing themselves on the glass cover. Whilst in this position I 

 availed myself of the opportunity of a closer inspection, and occa- 

 sionally mounted them in balsam. 



Up to this point I had not been able to guess what they were, 

 but now I obtained some scanty information. I saw that after 

 they were mounted the two hinder pairs of legs were not so appa- 

 rent as when the creature was alive. In most cases the position 



VOL. XI. B 



