The Journal of experimental zoology . Fig. 14 Records of rhythmic, spontaneous movements,marks five minute intervals. The base line. C P^ig. 15. Records of rhythmic, spontaneous movements. The base linemarks five minute intervals. 256 SELIG HECHT performance of a rhythmic contraction, Ascidia passes througha period during which a certain strength of stimulus fails to callforth a movement of the body. However, as this refractoryperiod passes by and the time approaches for the culminationof the next rhythmic movement, this same sub-liminal stimuluswill call forth not only the usual siphon
The Journal of experimental zoology . Fig. 14 Records of rhythmic, spontaneous movements,marks five minute intervals. The base line. C P^ig. 15. Records of rhythmic, spontaneous movements. The base linemarks five minute intervals. 256 SELIG HECHT performance of a rhythmic contraction, Ascidia passes througha period during which a certain strength of stimulus fails to callforth a movement of the body. However, as this refractoryperiod passes by and the time approaches for the culminationof the next rhythmic movement, this same sub-liminal stimuluswill call forth not only the usual siphon contraction, but also thebody contraction in advance of its scheduled time. The function of these rhythmic movements is by no meansclear. Their accomplishment of a partial discharge of the waterin the branchial sac would be intelligible if something else be-sides the water were also expelled. Ascidia, however, possessesan effective mechanism for avoiding just such a necessity. Thetentacles in the oral siphon screen out all but the smallest particleswhich come in with the water current. Everything that passesbeyond them is inc
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Keywords: ., bookauthorwi, bookcentury1900, bookdecade1910, booksubjectzoology
