i88o.] Working v. Fighting. 77 3 
the fauna of the West African islands above referred to, he 
agrees substantially with Wallace. 
With reference to the zoo-geographical classification 
adopted by our illustrious countryman, he remarks, how- 
ever, that it is scarcely possible to conceive a greater contrast 
than that existing between the fauna of Hong Kong, Amoy, 
or even Siam on the one hand, and that of Borneo, Java, and 
Sumatra on the other/ a distinction which is repeated in a 
very striking manner in the Phillippines, whose northern 
portion shows an unmistakable approach to the true 
Chinese type, whilst the southern islands point very de- 
cidedly towards Borneo on the one hand, and towards 
Celebes and Gilolo on the other. These features may be 
traced in the mammals, fish, reptiles, insedts, and very 
clearlv in the mollusks. What may be called the endemic 
fauna" of the islands occurs in its nearest approach to purity 
in the centre of the group. These characteristics he explains 
by oceanic currents and by the changes of the monsoons. 
He does not, however, suppose that affinities between locally 
remote faunas can be universally thus explained. 
We meet, further, with a criticism of Wagner’s “ Theory 
of Migration,” which Prof. Semper considers as not really 
in opposition to Darwinism, as its author supposes, but as 
therein included. It may be said, then, when Mr. Wallace 
declares that species can arise only where there is room for 
them, he gives all that is really valuable in this supposed 
new theory. 
Prof. Semper deals thoroughly with the vexed question ot 
hybridism, refuting seriatim the four positions of the old 
school, viz., that hybrids do not exist at all, save in a few 
exceptional cases ; that, if produced, they are always, or 
nearly always, unfruitful ; that hybridisation never occurs 
without human intervention ; and that species which have 
been known to produce fertile hybrids are^ mere varieties, 
morphologically but not physiologically distinct. All these 
popular delusions are completely shattered to pieces by the 
fadts here adduced, observed among mammals, birds, reptiles, 
fishes, insedts, and even mollusks. One of the most interest- 
ing cases is that of Tetrao medius , now known to be a hybrid 
between the great Tetrao urogallus (cock of the woods, or 
capercailzie) and the black-game, Tetrao tetrix, and which 
in many districts is fast superseding the latter. But the most 
important lesson hence to be learnt is that in hybrids there 
* It must here be remembered that Mr. Wallace places the former realms 
in the Indo-Chinese, and three latter in the Indo-Malayan sub-division of his 
Oriental region. 
