The evolution of this primitive tooth to the bicuspid and molar type has been explained by two theories: that of concrescence and that of differentiation.
Line of concrescence of the outer lamella of the left outer gill-plate with the left mantle-flap.
Line of concrescence of the reflected lamellae of the two inner gill-plates.
Line of concrescence of the inner lamella of the right inner gill-plate with the inner lamella of the left inner gill-plate.
The four orders now retained exhibit successive stages in the modification of the ctenidia by reflection and concrescence of the filament, but other organs, such as the heart, adductors, renal organs, may not show corresponding stages.
Anterior portions of these axes fused by concrescence to the wall of the body.
The mechanical result of the concrescence of the outer lamellae to the mantle-flap, and of the inner lamellae to one another as shown in section D, fig.
In the lateral view of the animal with reflected mantle-skirt and gill-plates, the line of concrescence of the inner lamellae of the inner gill-plates is readily seen; it is marked aa in fig.
The joints of the rays are sometimes broken up into polygonal plates which may further fuse with one another; concrescence of this kind may also affect the pieces which form the base of the fin.
That the concrescence of the radial supporting elements of the fin took place pari passu with the development of a strengthening dermal support of the fin margin was the view expressly formulated in my previous paper on this subject.
As soon as any form of Plagonida begins to produce meshes by concrescence of meeting branches of the spines, it passes over into a corresponding form of Plectanida.
The genus Stephanospyris exhibits the same peculiar armature of the semipinnate lateral feet as its ancestral genus Dorcadospyris, but differs from it in the concrescence of the distal ends of the feet, to form a complete foot-ring.
The genus Plectanium has been derived from Plagonium by concrescence of the meeting branches, and bears therefore to it the same relation that the preceding Hexaplecta exhibits to Hexaplagia.
Usually they are simple, rarely branched; the branches are always very irregular and exhibit a remarkable tendency to unite by concrescence (figs.
This ring has been produced by concrescence of the distal ends of the two large curved lateral feet of Dipospyris.
This is produced by the concrescence of meeting branches, which arise from spines of the inner shell.
The genus Hexaplecta has probably been derived from Hexaplagia by concrescence of the meeting branches of the six spines, and therefore has to it the same relation that Plectophora bears to Plagiacantha.
To my own arguments on the subject I may add those of Kupffer, who has very justly criticised His' statements, and has shewn that growth of the blastoderm in Clupea and Gasterosteus is absolutely inconsistent with the concrescence theory.
Moreover, were the concrescence theory true, the coalescing edges of the blastoderm might be expected to form an acute angle with each other, which they are far from doing.
The great dermal plates of many fishes have been formed by the concrescence of groups of such scales.
The sub-umbral ectoderm and that covering the manubrium undergo concrescence to form a single layer (fig.
D, E); the cavity between the two walls of the cup becomes reduced byconcrescence to form the radial canals (r.
The Cephalopoda are mainly characterized by the concrescence of the foot and head.
The concrescence of the three produces a Y-shaped plate with the single limb directed inwards and the two limbs outwards (fig.
In many other types the concrescences between the various parts of the gills are carried much further; the maximum of concrescence being perhaps attained in Anodon and Unio[107].
The genus Phatnacantha has been derived from the preceding Stauracantha by concrescence of the branches of the apophyses.
The third mode of junction, by central concrescence of all twenty spines, was formerly regarded by me as an important peculiarity, sufficient for the separation of subfamilies and genera (Monogr.
We derive Acanthochiasma from Acanthometron by concrescenceof every two spines opposite in one axis of the body.
A fourth and a very different mode of junction, quite sufficient for the distinction of different families, is the concrescence in pairs of every two opposite spines, lying in one diameter (in Acanthochiasma and Chiastolus).
We derive Chiastolus from Actinastrum by concrescence of every two opposite spines in one axis of the body (compare above, pp.
By this concrescence is formed a polygonal or roundish plate with two pores, pierced by the radial spine between them.
Sixteen diametral spines, derived byconcrescence of thirty-two radial spines, 321.
But as I now find this concrescence to be an accidental and inconstant peculiarity of some species, it no longer seems to me to be of generic importance.
In some cases this manner of derivation could even be observed in ontogeny, as Reichert had seen in the Newt, where certain bones in the roof of the mouth are actually formed by the concrescence of little teeth, (supra, p.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "concrescence" in a variety of sentences. We hope that you will now be able to make sentences using this word.
