738 The American Naturalist. [September 
excellent figures on the embryo, which tell the story of degen- 
eration of the eye from simple disease of the organ, the species 
being exposed to conditions of life strikingly different from 
those of its family living in the same bay. 
Before the discovery of the eggs, the youngest individual ever 
seen is represented in Pl. XXIII, fig. 7, its eyes being though 
small, yet distinct, and “ apparently functional." 
From these data it is obvious that future embryological 
study on cave animals will farther demonstrate their origin 
from ancestors with normal eyes. 
IV. THEORETICAL RESULTS BEARING ON THE THEORY or DE- 
SCENT, AND MORE ESPECIALLY ON THE NEOLAMARCKIAN 
PHASE OF THE THEORY, INCLUDING THE DOCTRINE OF 
THE TRANSMISSION OF ACQUIRED CHARACTERS. 
It is evident that the cases just cited afford the strongest 
possible proof of the theory of evolution in general, and do not 
militate against the truth of the Neolamarckian phase of the 
theory, which holds that by a change of environment, induc- 
ing disuse of the eyes, such variations, especially atrophy of a 
part or whole of the eyes and optic nerves and ganglia have 
become established, so as to result in the origin of new species 
and even new genera. 
In the case of the blind goby, the burrowing Callianassa, 
the blind shrimp of Adelsberg Cave, and, in fact, nearly, if not 
quite all the blind forms now known, it is easy to see that the 
causes of variation are quite direct and appreciable, and that 
we do not need to invoke the principle of natural selection. 
And this is the view of Darwin himself? 
Besides the factors of change of environment and of disuse, 
the influence of the isolation of these forms from their out-of- 
doors’ allies should not be overlooked. Take the case of the 
blind goby of San Diego Bay, or the Callianassa of Buzzard's 
Day. Living in habitats remote from their congeners, obvi- 
* In our work on the Cave Fauna of North America we have discussed the bear- 
ing of the facts of cave-life on the Darwinian and Lamarckian phases of evolution 
and have attempted to show that natural selection is inoperative in such cases as 
these, quoting Darwin's own words when referring to the loss of eyes in such 
animals: “ I attribute their loss wholly to disuse.” (p. 137-143). 
