82 
and metacone precede the protocone (Taeker). But the palæontolo- 
gical evidence is so overwhelming that the embryological differ- 
ences must be supposed to be of a secondary nature. The refer- 
ence to the Multituberculata is rather unfortunate, since the mul- 
tituberculate Neoplagiaulax (Lower Eocene) must be derived from 
the paucituberculate Microlestes (Upper Triassic), not vice verså. In 
Triconodon we find in the upper as well as in the lower jaw that 
of the three cusps the central one is the largest, being evidently 
the most primitive; in Spalacotherium and Amblotheriidæ this large 
styliform central cusp is seen to be displaced inwards above, out- 
wards below. We are, therefore, entitled to say that the protoconid 
is the antero-external cusp — as held also by Fleischmann and 
Råse — and the homologue of that, the protocone, is the antero- 
internal cusp. Fleischmann starts with the study of a modern 
tooth (Dasyurus) instead of a fossil one; therefore he erroneously 
asserts that the upper molaåar contains one element (entomere) more 
than the lower, whereas "exactly the reverse is the case, — that 
the lower molar contains one element more (talonid) than the upper 
in the carnivorous forms. Råse and Taeker investigate the ontogeny 
of a purely Cænozoic type, the quadritubercular molar, and claim 
by this to see a repetition of a condition of the Cretaceous period, 
the domination of the protocone. With the development of the 
erushing bunodont tooth the protocone was depressed to the level 
of the other cusps. — Råse's term "pentaconid” is referred. some- 
times to the paraconid, sometimes to the hypoconulid. 
Leche publishes in "Studien iber die Entwickelung des 
Zahnsystems bei den Såugetieren” 1892 several embryological tooth- 
examinations, but gives no real contribution to the question of tooth- 
phylogeny; he warns against too pretentious statements of tooth- 
philosophies based only on our recent knowledge of the dental sy- 
stem; it is not even proved that the mammalian tooth has originated 
from "a. conical reptilian tooth.” The complication of the teeth is 
caused not only by their use in masticating food, as some reptiles 
do so without showing any "development of the teeth, but — as 
