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SUMMARY OF CURRENT RESEARCHES RELATING TO 
organ to appear, and here they are seen in various larvae. There are 
other suggestions of a similar kind. 
Significance of the Proliferated Epithelium in the Foetal Mam- 
malian Jaw.* — Mr. E. Broom points out that the gum of a seventh 
month human foetus is covered, especially on the inner side, by a layer 
of epithelium many times thicker than that covering the adjoining 
mucous membrane. On serial section, it is found that, though this 
ridge of gum extends all round the alveolar margin, the thick coating of 
epithelium is only met with in the region of the incisors and canines. 
The suggestion readily offers itself that this epithelial protection is 
directly connected with the requirements of the young mammal in 
grasping and retaining the nipple, but as, within certain limits, the 
younger the foetus the greater the development of the epithelial ridge, 
one is led to think that the proliferated epithelium has a deeper signifi- 
cance than merely the strengthening of the gum during the short period 
of sucking. Even in the human foetus of ten weeks, there is a ridge of 
thick epithelium covering the incisor part of the jaws. A similar con- 
dition seems to exist in all the higher Mammals. In Marsupials the 
thick layer of epithelium passes back to the molar region, and differs 
from the typical mammalian condition in extending to and covering the 
inner part of the lips. Even in placental Mammals the epithelial arma- 
ture of the jaw is developed at such an early date as to suggest its being 
the remains of an ancestral horny beak. So far as we can make out, the 
most primitive mammal would appear to be derived from the higher 
Amphibians. As is well known, the larva of the Frog and of most of 
its allies is provided with a horny beak on the front of each jaw which 
fulfils all the requirements of teeth. It is highly probable that the 
jaws of Mammals likewise possessed beaks in their young stages, and the 
proliferated epithelium which arms the front of the foetal mammalian jaw 
may be supposed to be the remains of this. 
Development of Vessels and Blood in the Great Omentum of the 
Babbit.! — M. P. Francis comes to the conclusion that the vascular 
plexuses of the great omentum of the Eabbit grow at the expense of the 
terminations of the pre-existing vessels of collateral buds, and at that of 
independent vascular elements. The terminal extremities of the vessels and 
the buds are transformed into capillaries in three different ways. They 
are gradually hollowed out, or primitive vascular vacuoles are formed, 
which fuse later on, or there is a degeneration of the axial protoplasm. 
When a capillary terminates in a vascular bomb-like ending the artery 
and the vein of this swelling both arise from the capillary ; this explains 
why these two vessels are ordinarily close together. The existence of 
vaso-formative cells independent of the general vascular plexus is in- 
contestable. The vaso-formative cells have the same characters as the 
points of growth. A single cell may be sufficient to form a vaso-forma- 
tive plexus. The canalisation of the cells and the vaso-formative 
plexuses is effected by the formation of primitive vascular vacuoles, 
which secondarily fuse, or by the degeneration of the axial protoplasm. 
The vaso-formative plexuses are not the only ones which are found in 
* Ann. and Mag. Nat. Hist., xv. (1895) pp. 420-1. 
f Arch. Biol., xiii. (1895) pp. (1895) pp. 521-58 (4 pis.). 
