TAN DER HCEVEn’s ZOOLOGY. 
93 
have a good deal of information given us about feathers; but perhaps 
the most important contribution that has been made to science on this 
subject is by Engel (vide “ Proceedings of the Vienna Imperial Aca¬ 
demy of Science,” vol. xxiii.), “On the Development and Arrangement of 
Feathers.” He tells us that the arrangement of the feathers is connected 
with the progress of segmentation in the embryo, which precedes the 
development of the several parts, each of the divisions formed on the 
surface of the body by these processes becoming clothed with feathers 
independently of the other. In each division the development of the 
capsules proceeds from the circumference towards the centre, the ar¬ 
rangement of them following the outline more closely in proportion as 
they approach to this boundary. The formation of a series of capsules 
commences with the appearance of a thickened streak, which afterwards 
break up into divisions corresponding to the number of feathers. In 
each pair of contiguous streaks the roots are developed alternately, so 
that each capsule in one series is opposed to the space between two in 
the next, giving rise to a great variety of complicated geometrical 
figures. The feather appears in the first instance as a nearly rounded 
collection of cells, which becomes divided subsequently into two sphe¬ 
rical masses. The superficial cells coalesce with one another, both lon¬ 
gitudinally and transversely, so that the feather acquires a fibrous struc¬ 
ture. The growth of the feather takes place from the end by the 
development of a terminal bud, which forms a new one by transverse 
fission, and so on till the end of the feather has attained a certain de¬ 
gree of slenderness. Similar terminal buds then appear on the separate 
vanes of each feather, and these, by continued transverse fission, de¬ 
velop new terminal and lateral buds, which last constitute the bilateral 
fringe of the individual vanes. In the course of these processes there 
is no formation or repetition of cells, in the ordinary sense of the term. 
We are not sufficiently acquainted with bird literature to notice 
omissions of any great importance; but among recent works, of which 
we observe no notice, we may mention Cassin’s “Birds of Texas, Cali¬ 
fornia,” &c.; Count Henry von der Muehle’s “Monograph of European 
Sylvidae.” This latter is but a posthumous fragment of an intended great 
work. Philip Lutley Sclater’s work on the “ Tanagers” is in process of 
publication; and we have speedy promise of the first part of Dr. Brewer’s 
great work on “American Oology.” “Haumannia,” too, the organ of 
the German Ornithological Society, of which'Williams and Norgate are 
the London publishers, still makes its appearance every second month,— 
quite the perfection of a periodical: in its pages the reader may revel in 
bird lore, and find abundance to gratify his appetite in perusing the ac¬ 
counts of this most attractive class of living creatures. 
In the classification of the Mammalia full use has been made of 
Professor Owen’s views respecting the dental characters of the class; 
and the author regrets that the same Professor’s memoir on the charac¬ 
ters, principles of division, and primary groups of the class, should have 
been published too recently to admit of that general discussion of it by 
zoologists which he thinks ought to precede. 
