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Updated: May 31, 2025
Those which settled and tried to compete in this sort of life perished. We may have to except the ascidia, but they paid for their success by the loss of nearly all their vertebrate characteristics. The future progress of vertebrates depended upon their continual activity in the swimming life. And they were forced by their environment to maintain this.
Rare instances point to poor races, but the magnolias and lime-trees are often so productive of ascidia as to suggest the idea of ever-sporting varieties. I have seen many hundred ascidia on one lime-tree, and far above a hundred on the magnolia.
We may now turn to the embryology of the Ascidia, an animal that seems to stand so much lower and to be so much more simply organised, remaining for the greater part of its life attached to the bottom of the sea like a shapeless lump.
In some there is another gland besides the liver, and this is taken to represent the kidneys. The body-cavity proper, or coeloma, which is filled with blood and encloses the hepatic gut, is very narrow in the Ascidia, as in the Amphioxus, and is here also usually confounded with the wide atrium, or peribranchial cavity, full of water.
Arts practised by savages. Ascension, coloured incrustation on the rocks of. Ascidia, affinity of the lancelet to; tad-pole like larvae of. Ascidians, bright colours of some. Asinus, Asiatic and African species of. Asinus taeniopus. Ass, colour-variations of the. Ateles, effects of brandy on an; absence of the thumb in. Ateles beelzebuth, ears of.
We call this layer the blastoderm, and the sphere itself the blastula, or embryonic vesicle. This interesting blastula is very important. The conversion of the morula into a hollow ball proceeds on the same lines originally in the most diverse stems as, for instance, in many of the zoophytes and worms, the ascidia, many of the echinoderms and molluscs, and in the amphioxus.
Pétersbourg," Ser. vii, Vol. 19, No. 2, tells us that the nerve-ganglion of the ascidia lies on the side of the stomach, and on that account can not be homologous with the spine of the vertebrates, but that the cord in the larva of the ascidia is nothing more than a support for the tail in swimming, which afterwards disappears, as with many other larvæ.
In their more advanced mesoderm we find a few contractile longitudinal canals which force the blood through the body by their contractions; these are the first blood-vessels. Transverse section of the branchial gut. A of Balanoglossus, B of Ascidia. r branchial gut, n pharyngeal groove, asterisk ventral folds between the two.
In this way it is easily conceivable that peltate leaves are a frequent specific character, while ascidia are not, as they only appear in the special cases of limited adaptation, as in the instances of the so called pitcher-plants. The genera Nepenthes, Sarracenia and some others are very well known and perhaps even the bladderworts or Utricularia might be included here.
But the end of this tendril bears a well-formed urn, which however, is produced only after the revolving and grasping movements of the tendril have been made. Some species have more rounded and some more elongated ascidia and often the shape is seen to change with the development of the stem. The mouth of the urn is strengthened by a thick rim and covered with a lid.
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