226 REVIEWS. 
celeration and retardation of certain parts of the animal, during 
its growth, and Professor Hyatt previously * showed that the de- 
velopment of the individual Cephalopod is an epitome of the devel- 
opment of the cephalopods generally, and that the successive forms 
were produced with comparative suddenness. 
Previous to the appearance of Mivart’s work in this country the 
reviewer, in the present journal (vol. iv, p. 755), while remarking on 
the ancestry of the King Crab, Trilobites and other Branchiopoda, 
accounted for their origin rather by a process of acceleration and 
retardation, involving a more or less sudden formation of generic 
forms, than by the theory of Natural Selection, and offered several 
of the objections against Darwinism which appear in the work 
under review. The former law, probably in active operation dur- 
ing the earlier portion of embryonic life, accounts for the origin of 
the differences, while Mr. Darwin simply assumes an inherent ten- 
dency to variation. Cope’s law may account for the origin of the 
new forms, while Natural Selection apparently plays an entirely 
subordinate role, and even may be found to account merely for the 
preservation (as suggested by the Duke of Argyll) of the specific 
form, keeping it within limits by the survival of the fittest, and 
the lopping off of monstrosities and oe the checking of all ten- 
dencies to variation in a useless direction 
Mepicat Microscory.t— Dr. Richardson’s book is an exper- 
iment in an absolutely unoccupied field. Other works of somewhat 
similar nature are books for microscopists who are physicians ; 
this is a book for physicians who are not microscopists. Meagre — 
in its account of apparatus and inaccurate in its scholarship as 
it must be confessed to be, it is an earnest, straightforward and 
successful attempt to enable the practicing physician to make the 
microscope useful in his daily work. Some who use it for this pur- 
pose will be disappointed, for successful microscopical work requires 
a delicate tact and a mechanical ingenuity which are possessed by 
very few persons, and which are wanting to many even among 
physicians. Good microscopists, too, are developed, not made; 
Dp. Welt 5 aap esr 
th in the T iate Ce opods; 
Memoirs of the Boston Society of Natural spay 1866, and AMERICAN ea ape 
_ Vol. IV, pp. 230 
tA Hand- Biok: pe oti Microscopy. By pig G. erg M.D., Micr 
scopist to the Pennsylvania Hospital. 12mo, pp. 333. Philadel : J.B. Lippincott & 
review was prepared for a A date number, m its iiris was 
accidentally delayed. — Eps.] 
