382 
a 
whale is the biggest known mammal ; our gigantic sala- 
mander is the biggest known amphibian ; probably our 
sun-fish, our tunmies, our sharks, and our devil-fish, are 
each in their way larger than any previous fishes—one 
living shark actually attaining a length of forty feet. No 
fossil bivalve molluscs are, to my knowledge, as big as the 
common Mediterranean pinna, or as that giant clam, the 
tridacna, whose shell is so commonly used as a basin for 
fountains. In fact there are only two important groups, 
the birds and the reptiles, in which extinct species were 
much larger than existing ones ; and in these two groups 
the decrease is evidently due to the later supremacy of 
the mammalian type.” 
He then goes on to show that in many lines of 
descent we find groups of animals which have steadily 
been increasing in size from the earliest epoch of their 
appearance to the present day, as, for example, the 
horses, the deer, and the elephants. Evolution generally 
tends towards increase of size in dominant groups ; but 
when a group ceases to be dominant and begins to decay 
its bigger members die out. 
Equally interesting and suggestive are the discussions 
on colourand the colour-sense, @ propos of the “ Veronica” 
and the distribution of fishes, in “The carp pond”’ and 
“The mountain tarn”; but we pass on to the chapter 
devoted to “ The donkey’s ancestors ”—a charming sketch 
suggested by “a dear shaggy old donkey making himself 
perfectly happy upon a bare rocky hillside, upon four 
sprouting thistles, a bit of prickly carline, and three 
square yards of wet turf at the outcrop of a little spring.” 
Let us, however, pass by his pedigree (the same as that 
of his cousin, the horse), and see what Mr. Allen has to 
say about his intelligence, and the reason of it. 
“Donkeys are the final flower of long ages of native 
evolution, the natural head and crown of one great line of 
mammalian development. To doubt their intelligence is 
to impugn the whole conduct of nature, to upset the 
entire system of evolutionary psychology off-hand. 
Donkeys cannot help being clever, because they are 
the final survivors in the struggle for existence in one 
of the most specialised, most highly developed, and most 
dominant mammalian stocks. They do not represent 
mere stranded and struggling relics of older types, like 
the very silly kangaroos, and ant-eaters, and hedgehogs, 
which drag on a miserable existence behind the times in 
out-of-the-way holes and corners of the earth; they are 
one of the finest developments of one of the most success- 
ful branches of the great ungulate tribe. I feel a genuine 
respect for every donkey I meet, when I remember that it 
was the mere accidental possession of an opposable 
thumb that gave my ancestors a start over his in the race 
for the inheritance of the earth towards the very close of 
the tertiary period.” 
In reading this most entertaining and instructive volume | 
almost every page offers some suggestive remark or 
apposite illustration of the principle of evolution; and it | 
| subject, and a very full and practical explanation of 
| the objects of compass compensation and the methods 
is very rarely that we meet with anything to which excep- 
tion can be taken on the score of accuracy. It is perhaps 
doubtful whether monkeys are “intellectually in the very 
front rank of the animal world,” notwithstanding “ the op- 
posable thumb and the highly mobile trunk, with its tactile 
appendage, give these creatures an exceptional chance of 
grasping an object all round, and so of learning its | 
physical properties.”” I am myself inclined to think they 
are decidedly inferior to dogs, horses, and elephants. So 
the tracing cf man’s sense of colour to the fact of our pre- 
NATURE 
human ancestors having been attracted by the bright 
colours of the orange, blue, and crimson fruits of tropical 
forests appears doubtful, if not erroneous; because the 
colours of such fruits are no indication of their edibility for 
either man or monkeys, and there is no reason they should 
be so, since mammalia in eating the fruits would be likely to 
crush and destroy the vitality of the seeds. At all events 
many bright coloured tropical fruits are poisonous, while 
many that are eatable aie green and unattractive. Even 
among our native berries children who trust to enticing 
colour are apt to be poisoned by bitter-sweet or deadly 
nightshade. Neither is there any evidence that— 
“Up to the beginning of the tertiary period, large 
evergreens of what is now the tropical type covered the 
whole world as far as the very poles themselves. Green- 
land and Spitzbergen then supported huge forests of the 
same general character as those which now spread over 
Brazil and the Malay Archipelago.” 
Nor is Buffon’s idea—that organic life must have 
begun at the Poles, because on the surface of an incan- 
descent planet the poles would be the first part to cool 
down sufficiently to allow of the conditions under which 
alone life becomes possible—at all in accordance with 
the teachings of modern science, as Mr. Allen maintains 
it to be. For the first cooling of the surface would neces- 
sarily occur at a time when the whole of the water of the 
globe was in a state of vapour, and this vast aqueous 
atmosphere would so far prevent the heat of the sun 
from reaching the surface, and so equalise radiation that 
there need have been no cooling at the poles earlier than 
at the equator; and when subsequently the water was 
condensed and oceans were formed, these would equalise 
temperature over the whole surface, and render it pos- 
sible for life to originate at one part as well as at another, 
But these are very slight blemishes in so excellent a book, 
which is calculated to bring home to every reader how 
much of interest and novelty, of intricacy, of beauty, and 
of wonder, is to be found in the structure or history of 
the humblest plants or the most familiar animals; and 
also, how greatly the once-decried doctrine of evolution ~ 
has added to the ideal and poetic aspects of the study of 
nature. ALFRED R. WALLACE 
THE COMPASS 
Traité Théorique et Pratique de la Régulation et de la 
Compensation des Compas. Par A. Collet, Lieutenant de 
Vaisseau, Répétiteur a YEcole Polytechnique. Ouvrage 
publié avec l’Autorisation de M. le Ministre de la 
Marine. (Paris: Challamel Ainé, 1852.) 
HIS new treatise on the compass contains an admir- 
able account of the most recent work done on the 
adopted to secure it. It is founded on the author's trans- 
lation, now twelve years old, of Smith and Evans’ 
Admiralty Manual—made for the benefit of the French 
marine. That epoch-making book is however still the 
basis or substratum of Lieut. Collet’s new work. 
The practical part of the English book is fully given. 
M. Collet has added as much elementary mathematics 
and physics as he thinks may be useful to such seamen 
- [ Feb, 23, 1882 
