1885.] Progressive and Retrogressive. 14I 
be regarded as ancestral types which have survived to the present 
time, or whether, on the other hand, they be results of a process 
of degeneration, and therefore of comparatively modern origin. 
The question, in brief, is, whether these creatures presenting these 
features be primitive ancestors or degenerate descendants. 
In the first place let us define the meaning of the word degen- 
erate. - This must be done first from a structural or anatomical 
standpoint. Degeneracy may be defined as a loss of parts with- 
out corresponding development of other parts. All animals are 
degenerate in some respect or another, as, for instance, the Mam- 
malia in the small size of the pineal gland and of the coracoid 
bone ; so that degeneracy, as a whole, can only be affirmed where 
the sum of the subtractions is greater than the sum of the addi- 
tions. Function of the parts must, however, be consulted in this 
matter. We naturally regard sensibility as the highest of animal 
functions, and mind as the highest form of sensibility. There- 
fore development of organs of sensibility and sense and mind 
constitutes a better claim of progress than development of stom- 
ach or of skin. Since motion is under the direction of sensibil- 
ity, organs of movement have much to do with the question. 
When perfection in this respect conflicts with perfection of brain, 
in evidence of position, we naturally give the preference to the 
latter in deciding. Thus the ruminating mammals are much 
superior to man in the structure of their feet, teeth and stomach, 
yet we properly assign the higher position to the quadrumana 
and to man, on account of the superior complication of their brain 
structure, 
Palæontology has proven? what had been already surmised, 
at the development of animal organisms has been on lines of 
increasing specialization of parts. That is, in lines of increasingly 
perfect adaptations of structures to ends, or functions. In certain 
series of animals we witness steadily increasing perfection of 
mechanisms of the limbs for running; in others for digging; in 
others for flying. In the teeth we find increasing perfection of 
machines for grinding, for cutting or for seizing. In the brain 
the specialization has evidently been towards increased acuteness 
of perception, increased energy of action, and increased intelli- 
gence. Specialization does not, however, necessarily imply pro- 
gressive development. Adaptation may be to a parasitic or a 
1 Cfr. On the Evidence for Evolution in the History of the Extinct Mammalia ;’ 
Proc. Amer. Assoc, Adv. Sciences for 1883. 
