288 PROGRESS OF MICROSCOPICAL SCIENCE. 
student is only informed whether it is No. 7 or No. 3 objective he 
is to use. This might have done very well for Dr. Kutherford s 
own class alone, but as not a few teachers prefer to employ the objec- 
tives of Ross, or Powell and Lealand, or Smith and Beck, as being 
better than Hartnack's, there is an omission which we fear will tell 
against the volume. Then, again, why does the author, in referring to 
the three unquestionably best makers in this country, omit Messrs. 
Smith and Beck ? We may say, too, that his mode of teaching the 
student the estimation of the magnifying power he is employing is 
clumsy in the extreme. On this point he would have done well to 
have consulted Beale's excellent volume. We observe that some very 
valuable advice is given on the subject of epithelium, which shows 
that the writer is thoroughly practical : it is in reference to the 
question of killing the animal, which must not be done with chloro- 
form. One passage on p. 23 is not quite clear, in which the author, 
who has all along been speaking of Hartnack's object-glasses, says 
that a tissue is " most evident with a ^^th. lens." What does it 
mean ? And again, what is the use of describing for the junior student 
what he admits can only be seen with a power of lOOO diameters ? 
and even then his description is not quite clear as to direction of striaB 
in muscle, we mean, of course, clear to the young beginner. Further, 
Beale's glycerine and Prussian blue is referred to on p. 27, without 
any reference to where the description of its contents is to be found, 
though afterwards an account of it is given on p. 66. The best chapter 
in the volume is that in which the author's microtome is described 
and figured. In this he very fully explains his very useful instru- 
ment, which works so well that we quite agree with Dr. Rutherford in 
the opinion that the alterations proposed by others have been " but 
the reverse of improvements." In the author's observations on cements 
we think he has spoken wisely and well, and we think his last obser- 
vations to the student most valuable advice. We like the plan he has 
adopted of interleaving the book with pages of plain paper, on which 
the reader can write any remarks he may have to make. On the 
whole then, with these few disparaging sentences we have already 
written, we think the book is a valuable addition to our literature, 
which we trust to see much improved after the next edition has gone 
to press. 
PROGRESS OF MICROSCOPICAL SCIENCE. 
Microscopic Work of the ' Challenger.' * — Professor Huxley writes 
as follows to * Nature ' (August 19), enclosing a letter from Professor 
Wyville Thomson : — The following extracts from a letter dated Yeddo, 
June 9, 1875, addressed to me by Professor Wyville Thomson, will, I 
think, interest the readers of ' Nature ' : 
" In a note lately published in the ' Proceedings of the Royal 
* This note han been ''crushed out" of several successive uuinberd of the 
* M. M. j; 
