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about the human teeth and does not endeavour to compare the 
different tooth-types or to trace the palæontological evolution. 
Rost's paper "Phylogenie des Saugetiergebisses” 1883 is on 
the whole very good. It is more a philosophical than a compara- 
tively morphological and palæontological criticism of Baume's theory. 
— Baume's "law of reduction” is to him a misunderstanding; teeth 
are indispensable for the vertebrates and therefore not on their way 
to disappear; but the limiting of the teeth from the whole epidermis 
of the Selachia to the jaws of the Mammalia is explained by the 
law of localisation of function, the specialisation of certain teeth 
by the law of reduction of homogenous parts under the further 
development of remaining parts. The primeval type of the mam- 
malian teeth was the conical or cylindrical tooth with fangs, but 
without diastema. From the fact that the ever-growing tooth has 
the same shape at both ends it is not allowable to conclude that 
it is the most generalized, because a tooth which grows from an 
unchanged matrix must have the same form at all parts. The 
ever-growing teeth prove themselves to be more specialised than the 
teeth with fangs in being (often secondarily enlarged) sexual weapons 
Or in having assumed a special function (rodent dentition); they 
are never found fossilised in the mammalian orders where they 
have 10 recent representative. The Edentata are not a primitive, 
but an extremely modified order which originally has had teeth 
with fangs, as shown by the milk-teeth of Tatusia. — Rost does 
not try to compare the tooth-forms, as Baume did. 
Hitherto Cope had not been able to find a common point of 
View for all the forms of mammalian molars, but after the discov- 
ery of the Puerco-fauna ("Trituberculate type” 1883 and "Tertiary 
Vertebrata” 1884) he detected the fundamental type from which 
both the ungulate and the unguiculate teeth can be derived, the 
trituberculate type, and with great acumen showed the transforma- 
tion of this type to even the most complicated recent teeth. 
Lataste's paper "Étude sur la dent canine” 1887 is chiefly a 
Philosophical explanation of the term "canine”. In the same year 
