190 



DE J. jrUEIE ON THE FOEM AND STEUCTUEE 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. Manafus and its kindred are among those piquant 

 forms, fit food for speculation. Is it a retrograde, dwarfed, or undeveloped Elephant 1 

 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 difierentiation 

 yielding lines of demarcation to modern systematists 1 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 Manafus and three other genera sufficiently diflPer from other 

 known mammals, so that under the present aspect of classification they best constitute 

 in themselves a separate order, Sirenia. The Sirenia, howe\'er, gradate into extremes, 

 or rather may be tabulated thus : — 



Cetacea 



Pachtdbkmaia. 



According, therefore, as we contemplate either end of the lozenge-shaped area does 

 the consanguinity of the Sirenia trend towards marine or land animals. Manatus, in 

 the totality of its characters, tends more towards Pachyderinata 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 palaeontology, remnants of animals 

 are revealed, combining chai-acters 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, 

 Zeiiglodon, Sec. point to other radial lines of alliances. The labours of the veteran 

 Professor J. F. Brandt, in his " Symbolae Sirenologicse," 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. Soo. Nat. Hist. 1848-51, p. 209. 



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