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short hut nevertheless a good contribution, and Rock Structure is 
also very fully given. However, we think that the writer might 
have given less space to his article on the latter subject, and withal 
have composed a fuller paper. For instance, we think he should have 
avoided the quotations which he has made, and he should have read 
Forbes’ paper to which he has referred. By doing so he would have been 
able to attempt something better in the shape of classification than he 
has given. Rotation or cyclosis is a good paragraph ; but Rotatoria is 
certainly too short a contribution for the ‘ Micrographic Dictionary.’ 
We had expected a tolerably long paper on the wheel- animalcules, 
hut we are sadly disappointed, and we cannot urge a reason for this 
treatment of a class which is perhaps more than any other essentially 
the microscopist’s. Assuredly it is a mistake. Salivary glands is 
fairly done, and the notice contains allusion to Pfluger’s remarkable 
discovery (?) of the nerves, which run, so to speak, into the very 
secreting cells of the gland. Sarcina, too, is a good contribution, but 
we hardly agree with the writer in his supposition that when it is 
formed in any quantity in the stomach, it is perfectly harmless. Is it 
not the case that many instances of gastric catarrh arise solely from 
the presence of this alga in the stomach ? The Scales of insects is, we 
think, but poorly done, and Mr. Mclntire’s work is not at all fully 
given. Shell is fairly done, and so is Silica ; in this instance the 
writer has evidently considered carefully the researches both of 
Messrs. Slack and Sorby. Spermatozoa and Sphceroplea are excellently 
given, and will well repay perusal. The articles on Spiral structures 
in plants; Spores ; Staining tissues; Stomata; Vaucheria; Volvox, and 
Vorticella, are all good ; they are, as a rule, modern, concise, and to 
the point. But, on the other hand, Teeth is a paper by no means so 
fully dealt with as it merits ; indeed, much of this subject is totally 
left out. But our most severe remarks have to be made upon one, and 
only one contribution, that on the spinal cord. This is an eminently 
bad paper, which by no means gives even a reflex of the splendid 
work achieved, both at home and abroad, on this important subject. 
It is really the only exceedingly badly executed portion of the entire 
work ; but that it by no means indicates the great advance that has 
been made in this subject is but too evident. It were better to say 
nothing of the cord than to leave it and the brain in the condition 
in which they have been disposed of by whoever has had charge of 
this part of the Dictionary. And now we have to speak of the paper 
on Test objects, which, though it precedes some of the others, we have 
left to the last. On the whole, we look on this contribution as a very 
good one, for the remarks are terse and to the purpose ; and there is a 
good deal of practical information on the subject of objectives (though 
not on immersion ones), which will prove immensely useful to the 
student who is commencing to work with the microscope. Still we niust 
observe that the writer appears to us to state opinions in regard to 
the optical quality of penetration which are not universally held. Of 
course we may have misinterpreted his observations, but so far as we 
have been able to gather from his remarks (and in regard to angular 
apertures we thoroughly agree with him) we do not see the force of 
