Chap. VI. 
TRANSITIONS OF ORGANS. 
193 
their intimate structure closely resembles that of common 
muscle; and as it has lately been shown that Bays have 
an organ closely analogous to the electric apparatus, and 
yet do not, as Matteucei asserts, discharge any electri¬ 
city, we must own that we are far too ignorant to argue 
that no transition of any kind is possible. 
The electric organs offer another and even more 
serious difficulty; for they occur in only about a dozen 
fishes, of which several are widely remote in their 
affinities. Generally when the same organ appears in 
several members of the same class, especially if in 
members having very different habits of life, we may 
attribute its presence to inheritance from a common 
ancestor; and its absence in some of the members to 
its loss through disuse or natural selection. But if the 
electric organs had been inherited from one ancient 
progenitor thus provided, we might have expected that 
all electric fishes would have been specially related to 
each other. Nor does geology at all lead to the belief 
that formerly most fishes had electric organs, which 
most of their modified descendants have lost. The 
presence of luminous organs in a few insects, belong¬ 
ing to different families and orders, offers a parallel 
case of difficulty. Other cases could be given; for in« 
stance in plants, the very curious contrivance of a mass 
of pollen-grains, borne on a foot-stalk with a sticky 
gland at the end, is the same in Orchis and Asclepias,— 
genera almost as remote as possible amongst flowering 
plants. In all these cases of two very distinct spe¬ 
cies furnished with apparently the same anomalous 
organ, it should be observed that, although the general 
appearance and function of the organ may be the same, 
yet some fundamental difference can generally be de¬ 
tected. I am inclined to believe that in nearly the same 
way as two men have sometimes independently hit on 
