740 
still earlier period. It is clear, however, that the use of the word 
“regeneration” in such a case is only permissible, if at all, if its 
ordinary meaning be considerably extended. 
Naples, July 10th, 1892. 
Nachdruck verboten. 
The History and Homologies of the Human Molar Cusps. 
(A review of the contributions of Dr. A. Firiscumann, Dr. Junius Tanker 
and Dr. Cart Röse.) 
By Prof. Henry FAIRFIELD ÖsBoRn. 
Biological Department, Columbia College, New York. 
With 3 figures. 
The embryonic development of the cusps of the molar teeth in 
the Mammalia has lately been discussed in two very interesting papers 
by TAEkErR!) and Röse ?) and the homologies of the upper and lower 
cusps have been investigated by FLEISCHMANN 3). The work of the 
latter is based upon the comparative study of recent types of molars 
and the author reaches the conclusion that the system of homologies 
proposed by CopE*) and expanded by OsBorN 5) between the upper 
and lower molars is erroneous. 
TAEKER’S paper is chiefly devoted to the study of the succession 
and embryonic form of the molar cusps in different Ungulates: he 
supports by ontogeny the view based upon palaeontology that the 
ancestral cusps were conical; he shows that in the lower molars 
the ontogenetic order of development corresponds with the phylogenetic 
order as traced by Corr among the fossil forms but that in the upper 
molars the ontogenetic order does not correspond with the primitive 
phylogenetic succession as traced by Corr. Upon the whole however 
1) Zur Kenntnis der Odontogenese bei Ungulaten, Dorpat 1892. 
2) Über die Entstehung und Formabänderungen der menschlichen 
Molaren. Anat. Anz. 1892, Nr. 13 u. 14. 
3) Die Grundform der Backzähne bei Säugetieren und die Homologie 
der einzelnen Höcker, Berlin 1891. 
4) The mechanical Causes of the Development of the Hard Parts of 
the Mammalia. Journ. of Morphology 1889. Also earlier papers. 
5) The Structure and Classification of the Mesozoic Mammalia. Journ. 
Acad. Nat. Sc. Phila, 1888, p. 240; also: The Evolution of Mammalian 
Molars to and from the Tritubercular Type. American Naturalist 1888. 
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