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been developed to the stage of intelligence, or in the 
individual before it has grown to be an intelligent being. 
Mr. Romanes contends that some animals are too low 
in the zoological scale to be intelligent. He says :— 
“ Many instincts are displayed by animals too low in the zoological 
scale to admit of our supposing that they can ever have been due 
to intelligence. To give only one illustration. The larva of the 
caddice-fly lives in water and constructs for itself a tubular case 
made of various particles glued together. If, during its construction, 
this case is found to be getting too heavy—i.e., its specific gravity 
greater than that of the water—a piece of leaf or straw is selected 
from the bottom of the stream to be added to the structure ; and 
conversely if the latter is found to be getting too light, so as to 
show a tendency to float, a small stone is morticed in to serve as 
ballast. In such a case as this it seems impossible that an animal 
so low in the zoological scale can ever have consciously reasoned— 
even in the most concrete way—that some particles have a higher 
specific gravity than others, and that by adding a particle of this 
or that substance, the specific gravity of the whole structure may 
be adjusted to that of the water. Yet the actions involved are no 
less clearly something more than reflex ; they are instinctive, and 
can only have been evolved by Natural Selection.”—(.Mental Evo 
lution in Animals, ft. igi.) 
Now, in reply to this argument, we admit that it is a 
perfectly legitimate assumption, from the point of organic 
evolution, to take for granted that intelligence must have 
been developed, and that there must have been a stage 
at which the non-intelligent became the intelligent. But 
before we draw a definite line, and say with confidence 
that intelligence is only found above a certain grade of 
organic development, we must be sure that the facts of 
actual experience justify the assumption. Mr. Romanes 
says that the caddice-fly is too low in the zoological scale 
to be intelligent. What, then, is the position of this 
animal in the zoological scale ? It belongs to the class 
of insects. Are we to understand Mr. Romanes to assert 
that insects are too low in the upward path of develop 
ment to be intelligent ?