L. E. Robinson and J. Davidson 
23 
mount the integument of the dorsal and of the ventral surfaces 
separately. This is comparatively easy in the case of Argas persicus. 
At the line of junction between the dorsal and ventral marginal 
scutellae, the cuticle splits quite readily, and by inserting a fine needle 
obliquely under the skin, and passing it round the entire margin of the 
body, the two surfaces are separated and may then be removed by 
lifting the posterior margin with a pair of fine forceps, the muscular 
attachments being broken down progressively with the needle, as the 
cuticle is gradually and gently drawn forward. The two surfaces come 
away practically clean, any adherent tags of muscle being easily 
removed with the fine forceps, and an immersion of short duration in 
the potash solution is then sufficient to remove the soft jDarts of the 
capitulum and legs. Such preparations may be stained before mounting 
in Canada balsam, with picric acid in xylene, fuchsine, Bismarck brown 
or other stains, but this operation is really unnecessary if the prepa¬ 
rations have not received excessive treatment in the potash solution. 
The jDhotomicrographs which illustrate the structure of the cuticle (see 
PI. II, figs. 3 and 4) were prepared in the manner described above, 
and despite the fact that they are unstained, the details of the cuticular 
surface are faithfully rendered in the reproduction. 
In the study of minute parts, as the digit of the chelicera for 
example, preparations mounted in glycerine, glycerine jelly, Farrant’s 
medium, or monobromide of naphthalene, are useful adjuncts to the 
balsam mounts. 
It is very necessary to check all observations made on cleared, 
transparent specimens, wherever possible, by examinatioi:i of the same 
structure as an opaque object. The risk of misinterpretation of the 
appearances presented by cleared specimens, mounted in highly refrac¬ 
tive media, is enormous; and observations made on such specimens 
are a fertile source of the errors which have appeared from time to time 
in the published literature. 
Serial sections are indispensable if it is desired to form a complete 
idea of the structure of such a part as the capitulum of the tick. The 
technique which the authors have used for the preparation of serial 
sections of Argas persicus will be fully described in the second part of 
this paper, but it wull not be out of place to indicate the main principles 
now. 
Satisfactory fixation of the tissues is by no means easy to ensure in 
the case of Arthropods possessing a stout, highly chitinised integument. 
For the study of the chitinous parts and the general anatomy, provided 
