The Ascidian tadpole, young and gay, Doth Life with one bright eye survey, His consciousness has easy play.
In the second parcel, received this morning, there is a piece of Leptoclinum punctatum, and also part of anAscidian which appears to be A.
It is not only among cleavage-stages that they are to be found; you may also find them very clearly exhibited in our ascidian *Clavellina* for instance.
Another very typical case of a morphogenetic system of the harmonious type is supplied by the phenomena of restoration in the ascidian *Clavellina*.
Now this new organisation is not that of a branchial apparatus but represents a very small but complete ascidian (Fig.
Now all these difficulties vanish, if we consider the regeneration of animals, such for instance as many worms of the annelid class or our familiar ascidian *Clavellina*, in which regeneration in both directions is possible.
By means of this current the ascidian obtains food.
The ascidian when born is a tiny, free-swimming, tadpole-like creature with a slender finned tail.
An ascidian or sea-squirt from the coast of California.
Still a casual glance at the Ascidian tadpole shows that deficient as is the development of the ganglia afterward forming the medulla, the face is still more deficient.
The eye of the ascidian tadpole agrees fundamentally with the type of eye peculiar to the vertebrates in that the retina is derived from the wall of the brain.
The human cyclopean monstrosities, for example, might be regarded as reversions to the single-eyed sea-squirts, who are possibly the Ascidian precursors of the vertebrates.
By this view the tadpole of such Ascidian as Ciona, for example, represents more closely the common ancestor of the group than does any other form we know.
Now, in all the long line, from the ascidian upwards to man, nature had supplied none but physical wants.
I do not know that an ascidian jelly-bag has any other faculties than those of sucking in water, and of sticking to a stone.
If nature endowed an ascidian with the power of acquiring moral faculties, it was bound to use them as soon as it had got them.
He further observed the maneuvers executed by the crab to secure the attachment of an ascidian to its shell.
Faunt reversed the experiment, taking the ascidian away, when the crab deserted its quarters, found a shell with the ascidian on it, and occupied it very quickly.
Sometimes a large ascidian will wholly cover a shell; or several smaller ones will spread themselves over the same shell so as to form a continuous envelope over it.
Mr. Percival Wright, having taken the crab from a shell to which an ascidian had attached itself, found that the latter abandoned the shell in a short time.
As it grows, it resembles in every particular the ascidian larva, with which, indeed, Kowalewsky and Professor Ray Lankester have demonstrated its essential identity.
So that in this respect the ascidian larva is nearer to the original type than the tadpole or any other existing animal.
Thus, in spite of adult degeneracy in the ascidian and adult progress in the frog, both tadpoles preserve for us very nearly the original form of their earliest backboned ancestor.
The ascidian has only one eye inside its useless brain, while the tadpole and all other vertebrates have two from the very first.
Now, as the young ascidian has retained the ancestral position of his almost useless eye so steadily, it is reasonable to suppose that he has retained its other peculiarities as well.
Haeckel's, it may be well to consider what the degeneracy of the ascidian really means.
As an active ascidian again Fresh forms he began to contrive, Till he grew to a fish with a brain, And brought forth a mammal alive.
The tadpole and the ascidian larva divide between them the honour of preserving for us in all its native simplicity the primitive aspect of the vertebrate type.
Defn: Any compound ascidian of the genus Pyrosoma.
Defn: A pedunculatedascidian of the genus Boltonia.
Kowalevsky would have seen in the ascidian larva a common prototype of the vertebrate series; the followers of Von Baer would have popularised the embryological conception of the single origin of animal life.
It has already been shewn that from the dorsal and lateral portions of this section of the primitive alimentary tract the notochord and muscles of the Ascidiantadpole are derived.
The whole structure is probably homologous with the peculiar fold, usually prolonged into numerous processes, which normally projects from the dorsal wall of the Ascidian branchial sack.
It may be noted that the same difficulty is involved in supposing, as I have done, that the eye of the Ascidian Tadpole was developed from that of a Vertebrate.
In some other Ascidian types a few more facts about the mesoblast will be alluded to.
The Annelid theory of Dohrn and Semper was perhaps not so widely accepted as the rivalAscidian theory, but it counted not a few adherents and gave a certain stimulus to comparative morphology.
Amphioxus therefore might well be considered an extremely simplified and degenerate Cyclostome, and the ascidian larva the last term of this degeneration-series.
Such is, in my opinion, the nature of the homology existing between the tail of the ascidian tadpole and that of Amphioxus or of young amphibians.
For the later history of the Amphioxus-Ascidian theory the reader may be referred to A.
With the possible exception of the Ascidian theory, all the numerous theories of vertebrate descent suffered from this irremediable defect, and none carried complete conviction.
The ascidian larva, having no cilia and being necessarily motile, requires for the insertion of its muscles or contractile organs .
He pointed out also that the "notochord" was confined to the tail of the ascidian larva.
The ascidian with its distinct though simple nervous system is a different and much higher being.
The white threads seen in the ascidian are the earliest expressions of the white cords of the higher animals which every one knows as nerves.
The central mass contains much of very active protoplasm: it is for the ascidian the chief source of all nervous power and action, and is the simplest form of a so-called "nerve-centre.
The exigences of lives fuller than that of the ascidian demand, however, other movements, whose complexity is continually increasing as the scale of life is traversed.
Such movements as these in the frog or in the man are evidently similar to the wrigglings caused in the ascidian by the contact of an external bit of matter.
In the phylogeny of man, for example, what a vast hiatus yawns between the ascidian and the lancelet, and another between the lancelet and the lamprey!
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "ascidian" in a variety of sentences. We hope that you will now be able to make sentences using this word.
