B. G. Wilder on a jeetal Manatee and Cetacean. 113 
regarded as in the line of sirenian descent, that we may regard 
its influence as almost inappreciable as compared with the 
other. 
Further discussion of the subject is deferred until the fostal 
manatee has been dissected,* and until the writer is able to pre- 
pore a longer paper in which the various questions involved 
may be more fully presented. It is to be hoped that no oppor- 
tunity will be lost for peoering still earlier sirenian embryos and 
or preserving the membrane 
SUMMARY. 
The specimens hea manic cea are aian the smallest 
foe bi sirenian: and cetacean uring, if ex- 
tended, ‘085 (3-7 inches), and 0: 0B (2: 9 chet, iepeateely. 
The head of the manatee is strongly flexed upon the 
chest, and the tail forms a right angle with the trunk. 
e general aspect of the head and face of the manatee is 
ungulate rather than cetacean 
. To this extent the embryo of a lower form resembles the 
a of a higher. 
This, while contrary to the usually accepted rule, may be 
ay an exemplification of a more comprehensive law; namely, 
that the young of animals resemble their ancestors. 
6. This retrograde metamorphosis of the manatee points to 
a like retrograde evolution of the Sirenia from prior ungulate 
orms, 
7. This idea is confirmed by what is known of the geolonies 
succession of sirenian forms 
he determination of ‘the affinities of the Sirenia, is likely 
to be accomplished by the study of brains and embryos rather 
1an by minute osteological comparisons. 
AUTHORS CITED. 
1. phology ee On the form and structure of — Manatee | samgonebpspesk rag 
1. Soc., Lo _ 3, 1872. (Read Nov. 
Page 127-202; plates xvii — ( 
2. Brandt, J. : Symbol Sit Sirenologice. Fascic, iii, 1867-1868. 
3. Murra rray, Andrew : The geographical distribution of Mammals. London, 1866; 
quarto, pp. ee 2 2 plates, 101 ma 
4. Gervais, Paul: Addition au Mémoire par W. Turner de la placentation des 
1 sia, compare a celle des autres mammiféres. Journal de Zodlogie, 1872, Tom. 
pl. xv: 
5. Gray, J Eh: Notes on on the fostus of an elephant and of a hippopotamus in 
the collection of the British Museum. Proc. Zool. Soc., June 25th, 1868, 491. 2 
Wyman, ee: Remarks upon a foetal whale (Balena mysticetus) six 
inches Tong, roc. Boston Soc. Nat. Hist., 1850, 355. 
Rie ce t to throw light upon the development of the 
Po se per and of the vita heart; ape may solve the neetion os 
: F of cervical vertebrae, 0 which nt opinions are wholly contra- 
dictory (Murie, 1, 137). fet 
Am. Jour, Sox—Turp Ssnrtzs, Vou. X, No. 56.—AuGust, 1875, 
g 
