Natural-Historical Colleciions. 463 
step in this physiological investigation ; for, so far as he knew, they had not as- 
certained the function performed by any one of them. Dr. H. concluded by 
strongly recommending to Sir George Mackenzie, and other phrenologists, to 
pursue the truly philosophical, though very difficult course of inquiry which he 
had pointed out.” 
M. Strauss’ researches on the Anatomy of Spiders.—M. Strauss is already 
favourably known by his labours on the anatomy of insects, which the Academy 
of Sciences, in 1824, judged worthy of one of its prizes. With the intention of 
completing this beautiful work, this gentleman has continued to devote himself 
to the study of the organization of those articulated animals which are most near- 
ly related to the insects, and which were long confounded with them. 
These are the spiders, (arachnides,) and the other genera which are asso- 
ciated with them. Whatever may be the resemblance which the two classes 
present in their general form, there are, in many parts of their organization, dif- 
ferences So great as to separate them in the most decided manner. In the insects 
which are destitute of circulatory vessels, the atmospheric air penetrates into their 
interior by trachez, which diffuse it through all parts of the body, to bring it in 
contact with the nutritive humours: the air seeks for the blood. In the spiders, 
as respiration is performed by a special apparatus, the blood advances to the air. 
. From this single difference in the respiratory functions, numerous variations in 
the organization necessarily result. 
The respiratory system, therefore, presents the principal distinctive characters 
between the insects and the spiders, though M. Dumeril does not seem to ap- 
prove of the manner in which M. Strauss has formed this class. This naturalist 
composes it of three orders, in which are found the three modes of respiration, 
pulmonary, tracheal, and branchial. 
On continuation of his former memoir, M. Strauss has lately placed before the 
Academy an anatomical description of the tegumentary and muscular system of 
the Mygale avicularia, or bird-catching crab-spider, which the reporters have 
thought worthy of competing for the Monthyon prize of physiology. 
Geography of Plants.— Distribution of the Meliacee.—M. Adrien de Jusseiu 
has presented to the Academy of Sciences of Paris, a memoir on the family of 
Meliace@, upon which MM. Cassini and Desfontaines have pronounced a very 
favourable report. 
The essay is divided into three parts, the first of which, containing general ob- 
servations, is alone capable of analysis; the other two contain scientific descrip- 
tions of all the genera, and of many new species. 
M. de Jusseiu sen. had laid down, and happily applied the principle, that 
plants must be classed according to their affinities, by attributing different values 
to different orders of characters. M. Adrien de Jusseiu indicated another prin- 
ciple, which is now generally admitted, and which considerably modifies the pre- 
ceding; viz. that the value of characters, even in an elevated order, is not inva- 
riable in all families of plants. Hence it results, that instead of synthesis, ——in- 
stead of the rules hitherto established, a priori, for the determination of families, 
we must substitute analysis, which requires a minute examination of each parti- 
cular family. This has been undertaken by the author. The method is not new : 
almost all the monographs of the day are founded on it; but the execution, 
which must be considered the most difficult part, has never been treated with suc- 
cess equal to that of M. de Jussieu. 
M. de Jussieu in 1789, instituted the family of Melee previously con- 
founded by Adanson with the Pistacig. At the same period Cavanilles, treating 
of monadelphous plants, described and figured a great number of Meliacee ; and 
since that time, some other botanists have successively extended, or restricted, or 
regulated this group. Mr. Robert Brown, in 1814, proposed to separate from it 
a distinct family, undcr the name of Cedrelee; but M. de Candolle, in 1824, 
