from The Century Dictionary.
- noun The germinating or formative point in the yolk of an egg.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun biology The point, in the
yolkof an egg, from which the embryois formed
Sorry, no etymologies found.
Harvey described this little cicatricula as expanding under the influence of incubation into a wider structure, which he called the eye of the egg, and at the same time separating into a clear and transparent part, in which later on, according to him, there appeared, as the first rudiment of the embryo, the heart, or _punctum saliens_, together with the blood-vessels.
He first announced the general truth, "Omne animal ex ovo," and clearly proved that the essential part of the egg, that in which the reproductive processes begin, was not the _chalazæ_, but the _cicatricula_.
This flat germinal disk, which is round at first and then oval, and which is often described as the tread or cicatricula in the laid hen's egg, is found at a certain part of the surface of the large globular food-yelk.
This is seen on the yellow yelk-ball, at a certain point of the surface, as a small round white spot -- the "tread" (cicatricula).
By this first nutriment thus prepared for the embryon is not meant the liquor amnii, which is produced afterwards, nor the larger exterior parts of the white of the egg; but the fluid prepared, I suppose, in the ovary of viviparous animals, and that which immediately surrounds the cicatricula of an impregnated egg, and is visible to the eye in a boiled one.
And after the prolific dust is shed on the stigma, the seed becomes coagulated in one point first, like the cicatricula of the impregnated egg.
As the cicatricula of these eggs is given by the cock, and is evidently the rudiment of the new animal; we may conclude, that the embryon is produced by the male, and the proper food and nidus by the female.
At the same time it seems manifest, that those monstrous births, which consist in some deficiencies only, or some redundancies of parts, originate from the deficiency or redundance of the first nutriment prepared in the ovary, or in the part of the egg immediately surrounding the cicatricula, as described above; and which continues some time to excite the first living filament into action, after the simple animal is completed; or ceases to excite it, before the complete form is accomplished.