218 Natural-Historical Collections. 
forms the principal mass of the hemispheres. The third plane, which is the 
thinnest, has a similar extent with the second; but its direction is exactly op- 
posite, and its fibres, passing from the base of the corpus striatum, are employed, 
some to expand the temporal lobe, others to reach the cornu ammonis, and to 
continue with the corpora fimbriata to the fornix,—and lastly, to form the septum 
lucidum, or that portion which rises from the fornix to the corpus callosum. 
In young children, these three planes which terminate the peduncle, separate 
easily, and, so to speak, are only superjacent on each other. MM. Foville even 
believes, that, if at any time their adhesion is so great as to prevent the separation, 
it is to be attributed to a diseased alteration. 
M. Foville thinks that this theory of the structure of the brain explains the facts, 
that in nerveus diseases, free from complication, which effect the mental faculties, 
apparent lesion is always found in the cineritious matter of the convolutions, and 
that, when the locomotive powers alone are affected, lesion only takes place in the 
central and medullary parts. 
We observed, in 1827, that, after the repeated experiments of M. Geroux de 
Busareingues on the reproduction of animals, the sex of the product depends es- 
pecially on the relative vigour of the father and mother. This result has been 
positively confirmed. 
On the prismatic form in Mountain Rocks.—Unconnected with any theoretic 
views, it has long been known that many secondary rocks divide themselves into 
rectangular masses, or to speak more correctly into rectangular parallelopipeds : 
this is particularly the case in sandstones, in some limestones, and in coal. But 
the prismatic, form which basalt, of all mountain rocks, shows in the most charac- 
teristic manner, has given origin to much discussion as to how far that form was 
connected with igneous action. This property, it has been assumed, may arise 
chiefly from the predominance of argil. It has been found to take place in some 
varieties of marl and even argillaceous sandstones, substances which have evident- 
ly never been fused, and Bergmann has compared the columnar structure to the 
drying of starch. The striking examples of prismatic division which we have 
figured in this number, presentcoincidences which oppose these deductions. The 
specimens of Fig. 1. and Fig. 2. Plate V. were obtained from the vitrified fort of 
Craig Phadrick, near Inverness, on fracturing with the hammer a large mass of 
gneiss, whose exterior was converted into scoria, the more compact central parts 
divided into pretty regular prisms, with four and sometimes five or six planes. 
The specimen represented in Fig. 3. is from a bed of argillaceous ironstone, 
which had been elevated and distorted by a dyke of toadstone in a valley near 
Tideswell in Derbyshire. Here the prismatic form was remarkably perfect, 
the whole mass when in the vicinity of the toadstone, breaking into prisms from 
which we obtained some nearly regular hexagons. But while it thus becomes, 
from the first specimens, a certain fact, that the action of the heat will be a cause 
f this phenomonon ; and that we see produced, by a rock very generally consi- 
dered as volcanic, appearances which are repeated in lavas, in leucostines, or rocks 
with feldspathic bases, and trachytes or rocks with augitic or pyroxenic bases, 
still we have equal evidence of the same form being assumed under different cir- 
cumstances. Baron Humboldt, Messrs Jameson, Reuss, &c. have seen granites 
divided into prisms; D’Aubuisson has remarked a similar division in the euritic 
porphyries, which in Saxony are embedded in gneiss. It may be seen ina strik- 
ing manner in some of the Gypsum quarries of Montmartre, near Paris ; and rock 
salt in the mines of Northwich, presents the same appearances in great perfection. 
Hecatostoma ( Hecatoncotylus,) a new genus of parasitical worms, de~ 
seribed by M. Cuvier, before the Academy of Paris, llth October, 1629. 
—Amongst the intestinal, or parisitical worms, there is a certain number 
which have on the inferior surface, or at the posterior extremity of the body ; one 
or more organs in the form of suckers, more or less similar to these which we eb- 
serve upon the arms of the Sepiaria, orat the posterior extremity of the body of the 
