22 THE GENETIC RELATIONS OF THE CETACEANS. 
sustain an opinion one way or the other. It seems very safe, 
however, in view of the relations of the extinct faunas of that 
epoch to those of our own, to assume that it could not have been 
as late as the Cretaceous epoch. 
On so-called intermediate forms. — Dr. Brandt, in connection 
with the subject in question, has taught us how the genealogical 
record should and should not be sought. “The hypothesis of the 
derivation from earlier, older forms,” says he, ‘‘can only be proved 
with certainty directly from paleontology, and in no wise from 
so-called intermediate forms, which may have also originated in- 
dependently, neither can it be, by means of analogy, moiocdy 
deduced from isolated facts in the history of development.” 
Here again, I am happy to find that on the whole I have not 
been entertaining very different views from the eminent master, 
and I accept thè dictum (which I have often urged myself ) that 
the genealogical line can only be proved (in its details) by refer- 
ence to the actual forms, and that many so-called “ intermediate 
forms” are themselves dêrivatives from the same common progen- 
jtors (at different removes) as the more specialized types. 
‘But if it is really meant that the so-called intermediate forms 
do in no wise indicate the line and mode of descent of the more 
specialized types, I must for the first time differ, and differ decid- 
edly, from my eminent critic. Do the Prosimians afford no hint as 
to how the Simians have originated? None, the Hipparions, the 
Anchitheriids, and the Palotheriids for the Horses? . None, 
i Oreodonts and the Anoplotheres, for the Ruminants? None, 
the Marsupials and Monotremes for the mammals? None, thé 
Dinosaurians for the Birds? None, the Dipnoans for the Batra- 
chians? None, the Marsipobranchiates and the Leptocardians for 
the Fishes? But why enumerate more of the hosts that crowd 
upon the memory for almost equal recognition? If such interme- 
diate forms really give no clews or hints as to how more special- 
-~ ized and aberrant forms may have originated and developed, then 
_ indeed are facts in biology almost as barren and esac 
Minin proren paca ee E 
odum ee (imo forsan-adeo eocænam) Banania esse videntur. an, 
Symb. Siren +y 1868, 
oe *Die Annahme der Abstammung von friihern, ältern Formen kann nur direct auf 
Mittelformen, die auch selbstständige sein können, oder aus vereinzelten, der Ent- 
z  Wwickelur sgeschic te entlehnten Thatsachen auf dem Wege der Analogie indirekt 
