741 
he finds a very striking parallelism !) between embryogeny and phylo- 
geny both as to the form and succession of the cusps (see Table). 
Röse’s paper is also of great value in proving that in Homo 
and Didelphys, representing two widely separate classes, the em- 
bryonic history of the lower molars approximately repeats the ancestral 
history; he independently supports TAEKER in the conclusion that the 
upper molar cusps do not repeat the ancestral order assigned by the 
COPE-OSBORN theory, he therefore agrees with FLEISCHMANN that 
we have mistaken the history and homologies of the upper molar 
cusps, and suggests very courteously that the Ossorn nomenclature 
should be transposed to correspond with the embryological order; he 
further advances the original theory that the mammalian cusps have 
arisen not by additions to the single reptilian cone but by the fusion 
of a number of cones together. I will first consider the main prin- 
ciples involved in these papers and then mention some of the less 
important special points. The following table exhibits the correspond- 
ence and contrast between the phyletic and embryonic succession, as 
well as the homologies and order of appearance according to the 
COPE-OSBORN theory. 
(See Table page 742.) 
From this table the striking parallelism between ontogeny and 
phylogeny in the lower molars is brought out. Also the contrast 
between the early appearance of the hypoconid both in phylogeny 
and ontogenie and the late appearance of the hy pocone phylogene- 
tically and ontogenetically. 
1° That the primitive form of mammalian molar was 
a single cone to which all the other cusps have been 
successively added. I may first take up the different theory of 
cusp origin proposed by R6sE and observe that whatever support it 
may receive from embryology is offset by the overwhelming evidence 
of palaeontology. In figure 1, I have epitomized the slow trans- 
formation of the single fanged conical reptilian tooth (1), such as we see 
persisting in the Cetacea, into the low-crowned human lower molar (3). 
The first departure towards the development of lateral cusps is seen 
in the triassic Dromotherium (2); the second is in the contem- 
porary Microconodon (3); the third is in the jurassic Spalaco- 
therium (4); in the fourth (Amphitherium, jurassic) (5), 
we see the three cusps of the primitive triangle and the first 
1) See OsBorn, Odontogenesis in the Ungulates. Amer. Nat. 1892, 
p. 621. A fuller review of Dr. Tarker’s paper, 
