Agassiz, and showed that in Tornaria (the larva of Balanoglossus) a similar formation of body-cavities by pouch-like outgrowths of the archenteron took place.
The archenteron becomes the gastrovascular system or coelenteron.
Formation of archenteron and blastopore may, however, be deferred till a later stage (actinula or after).
After the isolation of the alimentary tract the remainder of the archenteron is formed of two cavities in front, which open freely into a single cavity behind (fig.
The archenteron gives rise to the epithelioid lining of both body cavity and water-vascular system.
The invaginated sack appears to be the archenteron and its mouth the blastopore.
A succeeding stage in which the primitive archenteron is commencing to be divided into three parts, the two lateral of which are destined to form the body cavity.
The hypoblast cells which form the wall of the archenteron grow with remarkable rapidity at the expense of the yolk; the spherules of which they absorb and digest in an amoeba-like fashion by means of their pseudopodia.
It arises as a prominence of six cells, projecting from the hypoblast at the anterior pole of the archenteron, and soon separates itself as a mass, or probably a pair of masses, lying freely in the cavity of the archenteron (fig.
Even while the invagination of the archenteron is proceeding, the larva becomes ciliated throughout, and assumes a somewhat conical form, the apex of the cone being opposite the flat ventral surface on which the mouth is situated (fig.
The archenteron is in part always converted into a section of the permanent alimentary tract and the section of the alimentary tract so derived is known as the mesenteron.
The archenteron always gives rise to outgrowths which form the peritoneal membrane and water-vascular systems.
The mesoblast appears to be formed of cells budded off from the anterior wall of the archenteron (Astacus, fig.
The thickening of the primitive germinal disc would, according to this view, be equivalent to the invagination of the archenteron in Astacus, Palaemon, etc.
The oesophagus first, and afterwards the rectum unite with the archenteron (fig.
The wall of the blastosphere next becomes invaginated, giving rise to an archenteron (fig.
The simple archenteron soon becomes anteriorly divided into three lobes, which communicate freely with the still single cavity behind (fig.
The forepart of the archenteron will later make the alimentary tract from the mouth to the middle of the duodenum, or small intestine beyond the stomach.
The epiblast now with its mesoblastic lining begins to form the Chorion, an embryonic intrauterine appendage; and the endoderm encloses the Archenteron or primitive gut.
The part of the archenteron that remains within the embryo proper begins in this third week to be moulded into the head-cavity.
The other part of the archenteron wall make the Allantois, the hind gut and the bladder.
In the tail the notochord is shewn at ch, the muscles at m, and the solid remnant of the ventral wall of the archenteron at dd'.
After the formation of the notochord and of the lateral muscles there remains of the archenteron in the tail only the ventral wall, which according to Kowalevsky forms a simple cord of cells (fig.
A, pp) which is subsequently continued into the region of the trunk, and forms the primitive body cavity, equivalent to the cavity originating as an outgrowth of the archenteron in Amphioxus.
The mesoblast originates in Amphioxus, as in several primitive invertebrate types, from a pair of lateral diverticula, constricted off from the archenteron (fig.
The mesoblast cells at the hinder end of the trunk, close to its junction with the tail, do not become converted into muscle cells, but give rise to blood corpuscles; and the axial remnant of the archenteron undergoes a similar fate.
Soon both the neurenteric canal and the caudal remnant of the archenteron become obliterated.
Part of the ventral wall remains as a solid cord of cells (al') The anterior part of the archenteron in front of the notochord passes wholly into the permanent alimentary tract.
The open end of this sack they regard as the blastopore--an interpretation which accords with my own, but they regard the sack as the rudiment of the allantois, and hold that it is equivalent to the invaginated archenteron of Amphioxus.
The whole dorsal wall of the posterior part of the archenteron is converted into the notochord (fig.
It ends anteriorly at the stomodaeum and posteriorly at the point where the solid remnant of the archenteron in the tail was primitively continuous with the branchial sack.
If we are justified in holding the body cavity of these forms to be a derivative of the primitive archenteron (vide pp.
The derivation of the mesoblast from the lateral walls of the posterior part of the archenteron is clearly comparable with the analogous process in Amphioxus.
The space occupied by the yolk corresponds to the archenteron or primitive digestive cavity; and the opening at the end to the primitive mouth or blastopore.
But our mid-intestine is still the greatly elongated archenteron of the gastrula.
Finally, we note two series of buds of cells, one on either side of thearchenteron in Figure 7 ii.
There is no yolk here to substitute epiboly (Section 9) for invagination, nor to obliterate the archenteron and the blastopore through its pressure.
Below the neural groove a thickening of the dorsal wall of the archenteron appears, and is pinched off to form a longitudinal rod, the precursor of the vertebral column, the notochord, shown in Figure 7 (n.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "archenteron" in a variety of sentences. We hope that you will now be able to make sentences using this word.
