PRESIDENTIAL ADDRESS. 503 
with in his monumental text-book and how little is there in others, even in text- 
books of Zoology ! 
Habt alle die Theile in der Hand, 
Fehlt leider nur das geistige Band—Life! 
We have become accustomed to the fact that like begets like with small 
differences, and from the accepted standpoint of evolution versus creation we no 
longer wonder that descendants slowly change and diverge. But we are rightly 
impressed when unlike comes to produce like, since this phenomenon seems to 
indicate a tendency, a set purpose, a beau idéal, which line of thought or rather 
imperfect way of expression leads dangerously near to the crassest teleology. 
But, teleology apart, we can postulate a perfect agreement in function and 
structure between creatures which have no community of descent. The notion 
that such agreement must be due to blood-relationship involved, among other 
difficulties, the dangerous conclusion that the hypothetical ancestor of a given 
genuine group possessed in potentiality the Anlagen of all the characters exhibited 
by one or other of the component members of the said group. 
The same line of thought explained the majority of human abnormalities as 
atavistic, a procedure which would turn the revered ancestor of our species into 
a perfect museum of antiquities, stocked with tools for every possible emergency. 
The more elaborate certain resemblances are the more they seem to bear the 
hall-mark of near affinity of their owners. When occurring in far-related groups 
they are taken at least as indications of the homology of the organs. ‘There is, 
for instance, a remarkable resemblance between the bulla of the whale’s ear and 
that of the Pythonomorph Plioplatycarpus. If you homologise the mammalian 
tympanic with the quadrate the resemblance loses much of its perplexity, and 
certain Chelonians make it easier to understand how the modification may have 
been brought about. But, although we can arrange the Chelonian, Pythono- 
morph, and Cetacean conditions in a progressive line, this need not represent 
the pedigree of this bulla. Nor is it necessarily referable to the same Anlage. 
Lastly if, as many anatomists believe, the reptilian quadrate appears in the 
mammals as the incus, then all homology and homogeny of these bulle is 
excluded. In either case we stand before the problem of the formation of a 
bulla as such. The significant point is this, that although we dismiss the bulla 
of whale and reptile as obvious homoplasy, such resemblances, if they occur in 
two orders of reptiles, we take as indicative of relationship until positive 
evidence to the contrary is produced. That this is an unsound method is 
brought home to us by an ever-increasing number of cases which tend to throw 
suspicion on many of our reconstructions. Not a few zoologists look upon 
such cases as a nuisance and the underlying principle as a bugbear. So far 
from that being the case such study promises much beyond the pruning of our 
standard trees—by relieving them of what reveal themselves as grafts instead of 
genuine growth—namely, the revelation of one or other of the many agencies in 
their growth and structure. 
Since there are all sorts and conditions of resemblances we require technical 
terms. Of these there is abundance, and it is with reluctance that I propose 
adding to them. I do so because unfortunately some terms are undefined, 
perhaps not definable; others have not ‘ caught on,’ or they suffer from that 
mischievous law of priority in nomenclature. 
The terms concerning morphological homologies date from Owen; Gegentsaur 
and Haeckel re-arranged them slightly. Lankester, in 1870, introduced the 
terms homogenous, meaning alike born, and homoplastic or alike moulded. 
Mivart rightly found fault with the detailed definition and the subdivisions of 
Homoplasy, and very logically invented dozens of new terms, few of which, if 
any, have survived. It is not necessary to survey the ensuing literature. For 
expressing the same phenomenon we have now the choice between Homoplasy, 
Homomorphy, Isomorphy, Heterophyletic convergence, Parallelism, &c. After 
various papers by Osborn, who has gone very fully into these questions, and 
Willey’s ‘ Parallelism,’ Abel, in his fascinating ‘Grundziige der Palaeobiologie,’ 
has striven to show by numerous examples that the resemblances or ‘adaptive 
formations’ are cases of parallelism if they depend upon the same function of 
homologous organs, and convergences if brought about by the same function 
of non-homologous organs. 
