FATEMAP OF FERTILISED EGG OF AMPHIOXUS: Conklin in studied the fate map of Amphioxus. In Tunguntung described the egg. Download Citation on ResearchGate | The Embryology of Amphioxus | Although the egg of Amphioxus is much more fluid and less stereotyped than that of. Edmund Beecher Wilson experimented with Amphioxus and Driesch were at the forefront of a movement in experimental embryology called.

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This is called blastula stage. On the dorsal side of the embryo, where the groove first appeared and where the streaming amphiixus cells into the interior of the embryo is the most active, a cavity is soon formed leading from the groove on the surface into the interior of the embryo.

Another impressive attribute of the vertebrates is the series of mesodermal somites, although it must be remembered that this is not exclusively chordate property, for some of the invertebrates, for instance the worms, possess it. The vegetal field, although more lightly colored than the animal hemisphere, is not entirely devoid of pigment, and the granules of pigment are, as in other parts of the embryo, situated mainly in the outermost parts of the bottle-shaped cells.

Book – Text-Book of Embryology 4

Amphioxus and the Mosaic Theory of Development. In this way the endoderm, the mesoderm, and the notochord disappear from the surface of the embryo into the interior where they belong. When the mesodermal crescent cells and notochordal crescent cells are totally shifted inside the lips of the biastopore will contract and the blastopore becomes very small. Already the simple alimentary system is confined to the interior of the organism, shut off from the outside except through an opening for the intake of food and output of waste.

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The original gastral mesoderm gives rise to perhaps not more than the first two pairs of somites. The outer layer of cells is the ectoderm which is in direct contact with the environment of the developing organism.

There is also a striking similarity to the distribution of different kinds of cytoplasm in the ascidian embryo. Diagram of a median sagittal section through an Amphioxus ovum. This contraction of the lips of the blastopore is connected with the disappearance of the mesodermal crescent material and the presumptive notochord from the rim of the cup-shaped embryo. The somites are block-like in shape and located lateral to the developing notocord and neural tube.

Thus a roof is made over the neural plate, with a small space between the two structures Fig. In other words, it consists of parts which have been classified as ectoderm.

The blastopore is very broad in the initial stage of gastrulation, but soon the lips of the blastopore amphloxus to contract, so that the opening which leads into the archenteron becomes smaller and is eventually reduced to an insignificant fraction of the original orifice. Privacy policy About Embryology Disclaimers.


During the period of cleavage the three regions become subdivided into blastomeres without the cytoplasmic substances having been displaced to any great extent. The embryo in this stage of development is called a gastrula. The embryo becomes ampjioxus shaped structures with two layer of cells. The mesoderm in Urodela detaches itself from the endoderm and moves forward between the ectoderm and the endoderm, having a free edge amphipxus but preserving an un-interrupted connection with the notochordal material on the dorsal side of the embryo.


The notochordal material becomes concentrated on the dorsal side of the embryo, as is the presumptive neural system, but to a much greater degree.

The outer ectoderm and inner endoderm with mesodermal notochordal crescent cells and central archenteron. In Amphioxus the neuropore persists until the mouth is formed.

Animal Cell and Enbryology Culture Amohioxus The division is slightly unequal, however, the result being two slightly smaller blastomeres and two slightly larger blastomeres Fig. The rim of the blastopore, however, continues to contract and at last covers the yolk plug altogether. More recently, the method of local vital staining has been applied to the study of Amphioxus development. The animal hemisphere is made up of cells containing the clear cytoplasm.

From vertical section through Amphioxus embryo with 5 primitive segments. The whole series of connective tissues is of mesodermal origin, and this applies even to the cartilaginous and bony skeleton. Quite considerable deviations from the pattern of urodele gastrulation are found to occur in frogs and toads.

However, in the amphibians this cannot be done by the bending inward of the vegetal region of the blastoderm, as in Amphioxus, because the vegetal wall of the blastula is far too thick and overladen with yolk and is therefore not capable of being bent inward as a whole. The opening of the archenteron to the exterior is called the blastopore.