1883 .] Compound Organisms and their Lessons. 19 
might say in every normal vertebrate animal down to the 
humblest fish — is his complete isolation from the rest of the 
world. He stands in no physical connexion with any other 
portion of matter, living or lifeless. He has certain well- 
defined boundaries, which even the least scientific observer 
cannot mistake. Of what takes place within that boundary 
he is conscious. Of what happens beyond his consciousness 
gives him no information.* 
Hence, as regards individuality or personality, the higher 
animals seem to contrast sharply with those minute and 
simple beings which are one with each other and with their 
quasi forefathers. But this contrast is only in seeming. 
There are stages or grades in individuality. There are ani- 
mals concerning which we must pause whether to pronounce 
them independent beings or parts of some larger totality. 
We may even be compelled to answer this question dif- 
ferently according to the point of view from which it is 
approached. The creatures in question are the so-called 
compound or “colonial ” organisms, of which the sponges, 
theHydrse, &c., — all, be it remembered, water-animals, — are 
familiar instances. Such an animal is at first produced from 
a single egg, and may thus claim in one sense to be regarded 
as a well-defined individual ; for whatsoever springs from one 
egg may fairly claim to be regarded as one animal, just as 
whatever springs from one seed is considered to be merely 
one plant, and not an indefinite number of plants. But the 
zoophyte — say the common Sertnlaria , or sea-fir, so called 
from its resemblance to the sprays of a fir tree — consists, 
again, of multitudes of animalcules, each resembling a 
Hydra. Each such animalcule captures food and digests it ; 
each ultimately dies, and is replaced by others which spring 
not from eggs, but from buds. Hence the question arises, 
Which is in reality the individual, the whole spray or the 
animalcule, — the product of original egg or each bud it has 
sent out ? Scientific zoology considers that the balance of 
evidence is in favour of the former view, and names the 
animalcules above mentioned “zooids.” 
But before coming to a conclusion we must consider some 
other cases of compound life. 
Remarkably curious and instructive is the green fresh- 
water sponge ( Spongilla ) found growing on woodwork im- 
mersed in water, such as piles and sluice-gates. It propagates 
* We do not intend to dogmatise on the question whether a person without 
any evidence passing through the medium of the senses can be diredtly aware 
of ideas or emotions occurring in the mind of another. To take up this subject 
would be a digression. 
