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thé valuable but intricate department of animal development. He 
further says, that he has been led to results differing somewhat from 
those of Retzius, so far as the physiology of the cellular tissues is 
concerned ; yet the general appearances exhibited and the manner 
of displaying them will remain, he adds, lasting memorials of the ta- 
lents and ingenuity of the Swedish Professor. 
The specimens to which Mr. Nasmyth’s attention has been directed 
form part of the collection of Mr. Koch, and they were delivered to 
him as belonging to Mastodon giganteum, Tetracaulodon Godmani, 
T. Kochii, T. Tapiroides, and the Missourium. In the analysis of each 
specimen he considers— 
Ist. The constituent structures of the tusk. 
2nd. The comparative extent of each of the constituent structures, 
as far as it can be ascertained. 
3rd. Hach constituent structure regarded separately in its minute 
and individual elements. 
4th. The conclusions derived from the premises as to the place 
which the animal should occupy in zoological: classifications: 
The principle upon which this mode of analysis is based, is that of 
the infinite variety which nature affects from limited materials, while 
the constancy of each variety throughout the same species is perfect. 
This constancy extends, Mr. Nasmyth observes, not only to the:con- 
stituent structures of each tooth, but to the extent of each constituent, 
as well as to the peculiar arrangement of the minute elements of 
which each of these structures is composed. 
The examination of each tusk evinces so marked and péculiar a 
structure, that a cursory inspection will, the author thinks, sufficiently 
demonstrate specific distinctions, which he supposes must have been 
accompanied by concomitant peculiarities of organization subser- 
In the following descriptions the word corpuscuie is used to desig- 
nate those appearances constituting the characteristic of bone, but 
denominated by Retzius cells, because the author is persuaded that 
those appearances are truly of a corpuscular character ; and the word 
cell is used to designate the structure of the interfibrous material 
which was left almost entirely out of account by Retzius, and de- 
scribed by others as structureless, but demonstrated by the author to 
be most characteristically organized in the different groups of ani- 
mals. The term fibres is used, moreover, to define those appeatances 
which Retzius considers due to a tabular structure, because the au- 
thor has been unable to find anything which confirms this theoretical 
appellation founded on the existence of 4 series of continuous rami- 
fying tubes. This question therefore he leaves in abeyance. 
Mastodon giganteum—The constituent structures of the upper 
tusks are only two, crusta petrosa and ivory. - The crusta pettosa, in 
the speciiens examined, is comparatively thin, or about halfa line ; 
but the extent of the investigation being necessarily limited, the au- 
thor considers that the observations on this head are incomplete. 
The corpuscules of the crusta petrosa are scattered irregularly ; but 
they are Humerous and give off radiating branched fibres, tending 
