89 
Adloff tries ("Zur Frage nach der Entwickelung der heutigen 
Såugetier-Zahnformen”” 1902) to reconcile the Cope-Osborn Differen- 
tiation Theory with the Råse-Kikenthal Concrescence Theory, neither 
of them being quite satisfactory while both of them contain several 
good points. .,,Wenn auch die Thatsachen, die [Kiikenthal & Råse] 
Zzunåchst. zur Begriindung ihrer Theorie ins Feld fihrten, zum Theil 
nicht hinausreichten, zum -Theil direct falsch waren, so schien doch 
damit ein Weg gegeben zu sein, der iiber manche unwabhrscheinliche 
Stellen der Cope-Osborn'schen Differenzierungshypothese hinweghelfen 
konnte." (pag. 364). Osborn's diagrammatic stages of transforma- 
tion are very seductive; but the haplodont stage is quite hypothe- 
tical among the mammals and the representatives of the protodont 
stage are far too few in number to fill the gap between the hap- 
lodont and the triconodont stage; Cope's explanation of the mecha- 
nical formation of the latter is quite problematic; it may rather be 
Supposed to have originated by fusion of single teeth which by the 
shortening of the jaws were drawn more closely together. And the 
transformation of triconodont teeth into tritubercular teeth is very 
improbable, transitional forms are totally wanting, and the rotation 
of the protocone is mechanically impossible (Råse). The reason 
why the outer cusps on both upper and lower teeth are the first 
to appear in the embryological development is not to be found in 
the degeneration of the protocone, but in the fact that the cusps 
belong to different dentitions which have coalesced, the outermost 
being the oldest. It is only from the tritubercular type onwards 
that the evolution is certain as indicated by Cope; we know of 
Undisputed examples of the growing-out of new cusps. — Several 
Objeetions can also be put forth against the Concrescence Theory. 
No doubt it is matter of fact that embryological fusions of neigh- 
bouring teeth of different dentitions do occur, and we may conclude 
from this that the process — perhaps together with fusion of teeth 
in the same longitudinal row — has played a part also in the 
bhylogenetic evolution; but it is not legitimate as Kikenthal does 
fo derive all mammalian teeth from the multituberculate teeth. If 
