x a a 
| 1887] . Zoology. 775 
that, in some cases at least, do not answer any definite purpose iR 
seems to me that there can be no reasonable doubt on the matter. 
_ Itmay be urged that we lack the knowledge to decide whether 
any given organism considered as a whole is or is not as good 
= asits nature admits. It may be urged that an essential element 
= of perfection is the due proportion of parts and faculties, and 
_ dividual. I have no desire to dispute the great truth underlying 
: these propositions, but in view of rudimentary organs alone, it 
would appear that, at least in some subordinate details, useless 
structures occur, and we have no means of deciding what limits 
to assign to the action of the causes producing them. It is 
certain that these appearances are not due to chance; there must 
5 some determining cause modifying the structure in this 
syay It is customary now to quote rudimentary organs 
and anatomical anomalies as evidences of descent, but it seems 
to me very improperly, occurring as many of them do quite out 
o ae L en aoe mee oe a he a 
5 za =. Katee ee ene aa ee ae 
Blan > h great modifications occur, the 
plan persists. No liberties, so to speak, are taken with it beyond 
mouth or four [sic] pairs of limbs. _ Is there reason to 
or analogous modifications, might not 
Yet I think every student 
ry would look on the suggestion that they will 
n. 
tens condense further these deductions, it appears that the in- 
co Sina Structure of any particular bone may show evidence 0 
: tat second, that of homology; 
at of correlation to the structure of other bones of the 
