The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . ded into threeregions—thorax, abdomen and post-abdomen. Testes numerous;vas deferens not spirally coiled. The chief genera are: Pharyngo-dulyon (Herdman), with stigmata absent or modified, containingone species. Ph. mirabile (fig. 28, C). the only compound Ascidianknown from a depth of looo fathoms, Polyclitium (Savigny), witha smooth-walled stomach; Aplidium (Savigny), with the stomachwall longitudinally folded (fig. 27); and Amaroucium (Milne-Edwards), in which the ascidiozooid has a long post-a
The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . ded into threeregions—thorax, abdomen and post-abdomen. Testes numerous;vas deferens not spirally coiled. The chief genera are: Pharyngo-dulyon (Herdman), with stigmata absent or modified, containingone species. Ph. mirabile (fig. 28, C). the only compound Ascidianknown from a depth of looo fathoms, Polyclitium (Savigny), witha smooth-walled stomach; Aplidium (Savigny), with the stomachwall longitudinally folded (fig. 27); and Amaroucium (Milne-Edwards), in which the ascidiozooid has a long post-abdomen anda large atrial languet. Family VI., Botryllidae.—Ascidiozooids having the intestineand reproductive organs alongside the branchial sac. Dorsal laminapresent; internal longitudinal bars present in branchial sac. Thechief genera are: Botryllus (Gaertn. and Pali.), with simple stellatesystems (fig. 28. D), and Boiry//{)rde5(Milnc-Edwards). with elongatedor ramified systems. It is well known that in the family Botryllidae,amongst compound Ascidians, the ectodermal vessels containing. (After Fig. 29.—Young Colony of Botryllus, showing Buds and Ampullae-a. Ampullae; B2 Bj, B4, Successive generations of buds;e. Stomach; i, Intestine; vp, Vessels of the test. 390 TUNICATA blood, which ramify through the common test and serve to connectthe vascular systems of the various members of the colony, havenumerous large ovate dilatations, the ampullae, upon their terminaltwigs (fig. 29). Various functions have been assigned to theseampullae in the past, and Bancroft has shown that m addition toacting as storage reservoirs for blood, organs for the secretion oftest matrix, and accessory organs of respiration, they are also organsfor blood propulsion. The ampullae execute co-ordinated pulsations,the co-ordination being due to variations in the was actually found that the ampullae could keep up the circula-tion for some time in a portion of a colony indep
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectencyclo, bookyear1910
