. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 282 A. S. PEAKSE. what to conform to the bilateral plan of structure and, as the radial nerv^es are not equally well developed, there is a dorso- ventral as well as an antero-posterior differentiation. In order to test the reactions of fragments of the body a series of experi- ments was carried out in which twelve TJiyoncs were each divided into two approximately equal pieces by a transverse cut. The two pieces of each animal were laid in a dish of sea water before a window in the position shown in Fig. 6. The ventral side o
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 282 A. S. PEAKSE. what to conform to the bilateral plan of structure and, as the radial nerv^es are not equally well developed, there is a dorso- ventral as well as an antero-posterior differentiation. In order to test the reactions of fragments of the body a series of experi- ments was carried out in which twelve TJiyoncs were each divided into two approximately equal pieces by a transverse cut. The two pieces of each animal were laid in a dish of sea water before a window in the position shown in Fig. 6. The ventral side of ^ > >. Fig. 6. Diagram to show the position in which animals were placed in the dish after being cut in two. The arrows represent the direction of the light, a, anterior end ; /, posterior end. the body was always placed uppermost and the long axis of the body was at right angles to the direction of the rays of light. The movements of the two halves were observed during the three hours following their separation and a summary of these reactions is given in Table III. Although the tube-feet were more or less Table III. Showing the number of anterior and posterior halves of twelve Thyoncs which gave different reactions. Locomotion. Righting. Nature of Reaction. Toward Light. Away from Light. Straight Ahead. None. Shadow. Number of anterior halves reacting 3 2 2 5 II 3 Number of posterior halves reacting 4 7 O I 12 9 active on both halves of the body in all cases, it will be seen that the posterior halves gave characteristic reactions more often than the anterior portions. They carried on normal spouting move-. 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 Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rat
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