1 •.)()() I MICROSCOPICAL JOURNAL. 323 



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sliow a marked tendency to change, as regards almost all 

 the organs of their body. The form-changes depend 

 mainly on the physico-chemical character of the medium. 

 The changes in individuals which live in salt solutions 

 subject to constant dilution with fresh water do not indi- 

 cate any transformation of Artemia into Branchipus ; 

 even those in the least salt solutions retain unchanged 

 the characteristics of their genus, especially in the male 

 sex. The concentration of the salt solution has certainly 

 an influence on the length of the post-abdomen, for in 

 dense solutions those with long post-abdomens predomi- 

 nate, in weak solutions those with short post-abdomens. 



Mechanical Stage for Diagnostic Microscope. — Mr. 

 Charles Baker has added to his "Diagnostic" microscope, 

 a detachable mechanical stage by which the whole of a IJ 

 inch X f inch cover-glass can be examined. The lower 

 plate fits on to the stage of the microscope, and has a ver- 

 tical movement thereon by means of runners, aided by a 

 screw at the top, which, however, gives movement in one 

 direction only. The screw at the side gives horizontal 

 movement for f inch both backwards and forwards, and 

 there is a gliding top plate which can be pushed over so 

 as to increase the travel for a further f of an inch. The 

 stage is thus well desig-ned for systematic examinations 

 over a large field. The price is $11. 



Method of Mounting in Canada Balsam. — It has not 

 only its comparative facility, but also it results in getting 

 the object close to the cover — a point that may be of im- 

 portance with high powers. It also insures the object re- 

 maining in position, very minute objects having a very 

 irritating tendency other-wise to be carried up to or be- 

 yond the margin of the cover-glass as soon as it is lower- 

 ed upon the slide. At the same time, in many cases it is 

 quite safe to mount the object directly on the slide. The 

 process is the same, except that it is generally carried 

 through in- one operation. A drop or two of balsam is 



