The Journal of experimental zoology . eginning of thecontraction. An analysis of the time relations of the phases of two separaterecords of the same siphon rim is given in the accompanyingtable (table 2). The two movements were made under thesame conditions within a few minutes of each other, and wereproduced by the same intensity of mechanical stimulus. Thesimilarity in the resulting records is very evident. Siphon TABLE 2rim cloture. Exp. DURATION OF PHASES, SECONDS 1 2 3 4 III 248 SELIG HECHT It will be noticed that the general shape of the curves produ
The Journal of experimental zoology . eginning of thecontraction. An analysis of the time relations of the phases of two separaterecords of the same siphon rim is given in the accompanyingtable (table 2). The two movements were made under thesame conditions within a few minutes of each other, and wereproduced by the same intensity of mechanical stimulus. Thesimilarity in the resulting records is very evident. Siphon TABLE 2rim cloture. Exp. DURATION OF PHASES, SECONDS 1 2 3 4 III 248 SELIG HECHT It will be noticed that the general shape of the curves producedby the closing and opening of the siphon rims resembles that ofthe contraction and recovery of smooth muscle (Winkler, 98).The effective agent in the closure is, indeed, the sphincter ofsmooth-muscle cells in the siphon working against the elasticityof the tissues and the test. Although the presence of the testundoubtedly helps in the opening of the rim, the recovery fromthe contracted condition can occur without the test. Animals. Fig. 9 Right side of animal with the test removed. A., heart; ^w., longitudinalmuscles; , transverse muscles. from which the test had been removed were still capable ofclosing and opening the siphons. It seems reasonable to supposethat the elasticity of the tissues which is responsible for thisrecovery is due to the presence of spaces filled with blood underpressure. 2. Body movements The bending of the body on its long axis occurs so that theright side of the animal always forms the concave surface of thebend. This is accomplished by the contraction of longitudinalmuscle strands which lie on the body wall of the right side only PHYSIOLOGY OF ASCIDIA ATRA LESUEUR 249 (fig. 9). In the living animal this side of the body adheres firmlyto the test. The left side, however, which includes the renalorgan, parts of the intestine, etc., is free from the test, the twobeing connected only by a single blood vessel. Consequentlyany contraction of the long
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Keywords: ., bookauthorwi, bookcentury1900, bookdecade1910, booksubjectzoology
