THE society's NOTE-BOOKS. 45 



bee than the genus Bombus. The Gamasi which infest the Dor- 

 beetle are ahnost identical with these. I generally mount them 

 in two ways — in Glycerine and in Balsam. Those mounted in 

 Glycerine are prepared in the following manner : — 



They are either killed by Cyanide vapour, or just wetted 

 w^ith spirit ; if put into spirit, they are not allowed to remain long 

 in it. They are then soaked for a day or two in x\cetic Acid, 

 until their legs become quite uncurled ; then for half-a-day 

 in water, and then in glycerine. They are mounted in a hol- 

 lowed slip with glycerine, to which two or three drops of Acetic 

 Acid has been added to each ounce of glycerine. This method 

 of mounting is intended to show the natural colour and shape. 

 The muscles are more or less destroyed by the acid, but some of 

 them can mostly be detected, and the natural position of the 

 chelae is generally well shown. 



Other specimens, after having been soaked in potash in the 

 usual way, and then double-stained in order to bring out certain 

 minute details, are mounted in Balsam, thinned with Benzole, 

 and without pressure. This method, in spite of what some have 

 said against it, I still consider greatly superior to the ordinary 

 process of using thick balsam. 



The structure of these mites is very interesting. Their 

 bodies are all in one piece, but there is an approach to a divi- 

 sion into two parts, as will be seen in Fig. i, where the cara- 

 pace is divided into two. The second pair of legs are very 

 curious. In some mites (Dermanyssus) the males have them 

 modified into claws, but in the females they are just the same as 

 the other legs. Although I have looked at perhaps 20 of these 

 Gamasi, I cannot detect any difference. I cannot say whether 

 all were males or all females, or whether they are hermaphrodite. 

 The feet are terminated by a claw and pad of the ordinary type, 

 but the claws are shorter than the pads. 



In Fig. I, by the mark x will be seen very curious organs, 

 which I have noticed in many, but not in all, mites. Mr. Tuffen 

 West seems to consider them trachese, and that the holes in 

 which they terminate are spiracles ; what they really are, I have 

 no idea, but I cannot think this supposition correct, because two 

 spiracles may be seen in the abdomen, w^hich are very evidently 

 spiracles, and which have no connection with, or resemblance to, 

 the other organs. They occur in just the same place as the 

 spiracles in ticks (Ixodes), to which ramifying trachese may be 

 seen adhering. 



The most interesting part of the mite is the mouth. This 

 is very difficult to understand, and in most specimens it is 

 nearly impossible to make out its details, wiiich can be seen only 

 with a i^-inch or jE^-inch objective. In the upper part of the 



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