Ouar. XV. 
ON THE DROSERACEA. 
357 
alimentary canal; but they live by absorbing through 
root-like processes the juices of the animals on which 
they are parasitic.* 
Of the six genera, Drosera has been incomparably 
the most successful in the battle for life; and a large 
part of its success may be attributed to its manner 
of catching insects. 
It is a dominant form, for it is 
believed to include about 100 species,t which range in 
the Old World from the Arctic regions to Southern 
India, to the Cape of Good Hope, Madagascar, and 
Australia; and in the New World from Canada to 
Tierra del Fuego. In this respect it presents a marked 
contrast with the five other genera, which appear to be 
failing groups. 
Dionza includes only a single species, 
which is confined to one district in Carolina. 
The 
three varieties or closely allied species of Aldrovanda, 
like so many water-plants, have a wide range from 
Central Europe to Bengal and Australia. 
Droso- 
phyllum includes only one species, limited to Portugal 
and Morocco. Roridula and Byblis each have (as I 
* Fritz Miller, ‘Facts for Dar- 
win,’ Eng. trans. 1869, p. 139. The 
rhizocephalous crustaceans are 
allied to the cirripedes. It is hardly 
possible to imagine a greater dif- 
ference than that between an ani- 
mal with prehensile limbs, a well- 
constructed mouth and alimentary 
canal, and one destitute of all 
these organs and feeding by ab- 
sorption through branching root- 
like processes. If one rare cirri- 
pede, the Anelasma squalicola, had 
become extinct, it woull have 
been very difficult to conjecture 
how so enormous a change could 
have been gradually effected. 
But, as Fritz Miiller remarks, we 
have in Anelasma an animal in 
an almost exactly intermediate 
condition, for it has root like pro- 
cesses embedded in the skin of the 
shark on which it is parasitic, and 
its prehensile cirri and mouth (as 
described in my monograph on 
the Lepadide, ‘Ray Soc.’ 1851, 
p. 169) are in a most feeble and 
almost rudimentary condition. 
Dr. R. Kossmann has given a very 
interesting discussion on this 
subject in his ‘Suctoria and Le- 
padide,’ 1873. See also, Dr. 
Dohrn, ‘Der Ursprung der Wir- 
belthiere,’ 1875, p. 77. 
t Bentham and Hooker, ‘ Genera 
Plantarum.’ Australia is the me- 
tropolis of the genus, forty-one 
species having been described 
from this country, as Prof. Oliver 
informs ine. 
