1864. | Jurvon’s Birds of India. 177 
also published a series of illustrations of Indian birds,* in a quarto 
volume of fifty plates, in which many rare species were figured for the 
first time. Besides this, he has contributed many papers relating to 
Indian zoology to different scientific journals, and has been a most 
indefatigable explorer and collector in nearly every province of India, 
It cannot be doubted, therefore, that Dr. Jerdon’s qualifications to 
carry out the plan he now proposes,—that is, to issue a series of Manuals 
of the Natural History of the Vertebrated Animals of India,—are very 
considerable. And looking to the way in which he has commenced to 
execute his plan, in the case of the two volumes now before us, which 
form the first part of his ‘ Manual of Indian Ornithology,’ we have 
every reason to be satisfied that it has fallen to his lot to undertake 
it. Nor can it be doubted that such a series of manuals is a great de- 
sideratum. At present, as Dr. Jerdon observes, to “ obtain acquaint- 
ance with what is already known respecting the Fauna of India,” it is 
necessary to “search through the voluminous transactions of learned 
societies and scientific journals,’ which are of course quite inacces- 
sible to residents in an Indian up-country station, and hardly to be 
referred to even in Madras or Calcutta. Dr. Jerdon’s aim, therefore, 
is to supply in a few portable volumes the information requisite for a 
student of any branch of the natural history of the vertebrata of 
India to ascertain what is already known of his favourite science 
and to what points especially he should direct his inquiries. The 
two volumes already published by Dr. Jerdon take us through the 
greater part of the class of birds; a third volume, shortly to be issued, 
will complete this part of the subject. The author will then turn his 
attention to the Mammals, Reptiles, and Fishes, and treat of each of 
these classes of animals in a similar manner. 
Dr. Jerdon introduces himself to his readers in the first volume of 
his present work with a well-written chapter of general remarks, which 
will repay perusal. After giving an outline of the structure of birds, 
external and internal, and some remarks on their migration, he pro- 
ceeds, before entering upon the subject of classification, to devote a 
few words to the much-vexed question of the differences between 
species and variety. A species, Dr. Jerdon defines as consisting of a 
“number of individuals closely resembling one another in size, struc- 
ture, and colour, and propagating a like race ;” a variety, as “ consist- 
ing of one or more individuals resembling certain other individuals 
sufficiently to be considered identical in species, and yet differing in 
certain external points of colour, size, or form.” As regards the mode 
in which this difficult subject, as encountered in the case of the birds 
of India, has been dealt with, the following remarks of our author may 
prove of interest :— 
“Some naturalists believe that permanent varieties are common in the 
animal kingdom, and Kaup calls them swb-species. Such persons consider 
that their differences from other individuals, of what they would term the 
typical form, do not entitle them to the full rank of a species. Others, 
again, deny that permanent varieties exist, and state their conviction that 
* «Tllustrations of Indian Ornithology” By T.C.Jerdon. Madras, 1844. 
1 vol. 4to. 
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