An ordinary meroblastic ovum consists then of a small disc at the formative pole, known as the germinal disc, composed mainly of protoplasm in which comparatively little food-yolk is present.
A meroblastic segmentation might perhaps be even more easily derived from the type found in Insects.
Such nuclei are formed in all craniate meroblastic ova[52].
This material forms a disc equivalent to the germinal disc of meroblastic vertebrate ova.
It is clear that it is not possible in centrolecithal ova to have any type of segmentation exactly comparable with that of meroblastic ova.
It must be admitted that the general evidence at our command appears to indicate that the nuclei of the yolk inmeroblastic ova originate spontaneously.
In most if not all meroblastic ova there appear during and after segmentation a number of nuclei in the yolk adjoining the blastoderm, around which cells become differentiated.
These types are not sharply separated, but form an unbroken series, commencing with the ovum which segments uniformly, and ending with the meroblastic ovum.
It is equally clear that the part of meroblastic ova which does not undergo segmentation is not a new addition absent in other cases.
In most existing Teleostei, the ovum has become again reduced in size, but the meroblasticsegmentation has been preserved.
The segmentation, though complete, approaches the meroblastic type more nearly than the segmentation of the frog's egg.
The earlier phases of the segmentation are like those of meroblastic ova, in that the furrows only penetrate for a certain distance into the egg.
The Teleostei, which have in common a meroblastic segmentation, had probably a Ganoid ancestor, the ova of which were provided with a large amount of food-yolk.
The segmentation, as in the Sturgeon, is complete, but approaches closely the meroblastic type.
The segmentation has the normal meroblasticcharacter (fig.
The occurrence of a meroblastic segmentation, in spite of the ovum being usually smaller than that of Amphibia and Acipenser, etc.
I have compared twomeroblastic eggs of the two classes respectively, because the scorpion's egg is meroblastic.
Take, again, a meroblastic vertebrate egg as of the bird.
Hertwig and Samassa show that by centrifugalizing, stimulating, and breaking down of large spheres the holoblastic amphibian egg may be converted into a meroblastic one, and then development will proceed regularly, i.
This is comparatively easy in the small meroblastic ova which contain little nutritive yelk--for instance, in the marine ova of a bony fish, the development of which I observed in 1875 at Ajaccio in Corsica.
This is the case with allmeroblastic vertebrates, most fishes, the reptiles and birds, and the oviparous mammals (the monotremes).
The meroblastic ova are only found in the larger and more highly developed animals, and only in those whose embryo needs a longer time and richer nourishment within the foetal membranes.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "meroblastic" in a variety of sentences. We hope that you will now be able to make sentences using this word.
