288 CONCLUDING REMARKS [Cuar, XV. 
genera are provided with such small roots,* and that Aldro- 
vanda is quite rootless; about the roots of the two other 
genera nothing is known. It is, no doubt, a surprising fact 
that a whole group of plants (and, as we shall presently see, 
some other plants not allied to the Droseraceæ) should 
subsist partly by digesting animal matter, and partly by 
decomposing carbonic acid, instead of exclusively by this 
latter means, together with the absorption of matter from 
the soil by the aid of roots. We have, however, an equally 
anomalous case in the animal kingdom ; the rhizocephalous 
crustaceans do not feed like other animals by their mouths, 
for they are destitute of an alimentary canal; but they live 
by absorbing through root-like processes the juices of the 
animals on which they are parasitic.t 
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, 
*(Fraustadt (Dissertation, Breslau, cirripede, the Anelasma squalicola, 
1876) shows that the roots of Dionwa had become extinct, it would have 
are by no means small. In another been very difficult to conjecture how 
Breslau Dissertation (1887) Otto so enormous a change could have 
Penzig shows that the roots of been gradually effected. But, as 
Drosophyllum lusitanicum are also Fritz Müller remarks, we have in 
well developed. Pfeffer (‘Landwirth. Anelasma an animal in an almost 
Jahrbucher, 1877) points out thatthe exactly intermediate condition, for it 
argument from the small develop- has root-like processes embedded in 
ment of roots in some carnivorous the skin of the shark on which it is 
plants is valueless, because the same parasitic, and its prehensile cirri and 
state of things is found in many mouth (as described in my monograph 
marsh and aquatic plants which on the Lepadide, ‘Ray Soc.’ 1851, 
neither catch nor digest insects— p. 169) are in a most feeble and 
F. DJ almost rudimentary condition. Dr. 
+ Fritz Müller, ‘Facts for Darwin, R. Kossmann has given a very in- 
Eng. trans. 1869, p. 139. The rhizo- teresting discussion on this subject 
cephalous crustaceans are allied to in his ‘Suctoria and Lepadidæ, 1873. 
the cirripedes. It is hardly possible See also, Dr. Dohrn, ‘ Der Ursprung 
to imagine a greater difference than der Wirbelthiere,’ 1875, p. 77. 
that between an animal with pre- } Bentham and Hooker, ‘Genera 
hensile limbs, a well-constructed Plantarum.’ 
mouth and alimentary canal, and one tropolis of the genus, forty-one 
destitute of all these organs and species having been described from 
feeding by absorption through branch- this country, as Prof. Oliver informs 
ing root-like processes. If one rare me. 
Australia is the me- 
