. Elementary text-book of zoology. ASCIDIA. 293 Asddia is hermaphrodite. The testes and ovaries are _. ,^, simple paired sacs lying over the stomach KeproductlTe. 1 1 1 • i_ t • 1 and leading by separate ducts into the atrium. The main interest attaching to Ascidia is involved in its development. If the anatomical account has been carefully Fig. 205.—Development of an Ascidian. (Afler KOWALEVSKI.) Blastula, Gastrula. Blastocoele. Hypoblast. Neuropore. Neural Tube. The various stages are shown in median section. followed, it will have been noticed that Ascidia differs from Developm
. Elementary text-book of zoology. ASCIDIA. 293 Asddia is hermaphrodite. The testes and ovaries are _. ,^, simple paired sacs lying over the stomach KeproductlTe. 1 1 1 • i_ t • 1 and leading by separate ducts into the atrium. The main interest attaching to Ascidia is involved in its development. If the anatomical account has been carefully Fig. 205.—Development of an Ascidian. (Afler KOWALEVSKI.) Blastula, Gastrula. Blastocoele. Hypoblast. Neuropore. Neural Tube. The various stages are shown in median section. followed, it will have been noticed that Ascidia differs from Development, "^^""ly ^^^ ^he preceding types in having the nervous system confined to the dorsal region 01 the body, in possessing numerous paired slits in the wall of the pharynx, and in the presence of a ventral heart, which is (in- termittently) respiratory, involving a backward current in the dorsal vessel and a forward in the ventral. These are all characters in which the Tunicata resemble the other members of the important phylum Chordata. In addition, in the structure of the pharynx, the method of feeding and the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Masterman, Arthur Thomas. Edinburgh, E. & S. Livingstone
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