190 DR. J. MURIE ON THE FORM AND STRUCTURE OF THE MANATEE. 
misty film which here and there drapes some with tantalizing indefiniteness (leaving 
them like islands and peninsulas, sea-girt, or but narrowly connected to the, so to say, 
mainland of typical forms), we should be astonished, and bow in reverence to that fiat 
which has planned and carried out such a grand design. Probed to its entirety and 
ramifying links, each vertebrate might yield a life’s study; but the more fascinating 
to biologists of all times have been those strange and uncouth types, leading to all 
manner of fanciful conjectures. MJanatus and its kindred are among those piquant 
forms, fit food for speculation. Is it a retrograde, dwarfed, or undeveloped Elephant? 
a “true embryonic type of Pachyderms,” as the elder Agassiz’ puts it. Is it a partially 
converted Cetos? Is it the reflex of unknown and antedated swarms of mammals of 
intermediate organization, which would fill up the chasms of structural differentiation 
yielding lines of demarcation to modern systematists? Such interrogations, to be 
answered satisfactorily, require a more comprehensive knowledge of the embryology 
of Pachyderms and Cetacea, a far greater acquaintance with allied fossil forms, a 
better appreciation of what constitute transitional links, and a further profound 
investigation into the principles of the doctrine of evolution. These gaps in science 
necessarily limit generalization, and cause reply to be theoretical. The most that can 
solidly be affirmed is that Manatus and three other genera sufficiently differ from other 
known mammals, so that under the present aspect of classification they best constitute 
in themselves a separate order, Sirenia. The Sirenia, however, gradate into extremes, 
or rather may be tabulated thus :— 
CETACEA R 
hytina. SIRENIA. Halitherium. PACHYDERMATA. 
Hatlicore. , 
According, therefore, as we contemplate either end of the lozenge-shaped area does 
the consanguinity of the Sirenia treud towards marine or land animals. Manatus, in 
the totality of its characters, tends more towards Pachydermata than Cetacea; but 
in its individuality we cannot strictly say it belongs to either, or predict its being 
an embryonic type of the former. Between each two of the three above orders are 
wide intervals. Still, with our scanty knowledge of paleontology, remnants of animals 
are revealed, combining characters which we are apt to consider appertain but to one. 
Moreover the relations of the Sirenia are not solely bound by the two orders given, 
although these seem more direct in their affinities. Such aberrant types as’ Trichechus, 
Zeuglodon, &c. point to other radial lines of alliances. The labours of the veteran 
Professor J. F. Brandt, in his “Symbol Sirenologice,” are most copious in com- 
parisons of the like kind; but with all his conclusions as regards Manatus and its 
allies I do not coincide. The above diagrammatic view I believe expresses the probable 
kinship of the Sirenian genera one to the other; but to give full reasons therefore would 
* Proc. Bost. Soc. Nat. Hist. 1848-51, p. 209, 
