. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. COPULATION IN A TURBELLARIAN WORM. 299 or whether the spermatozoa may not be deposited in the atrial cavity of each worm and an exchange of them be effected by simple apposition of the pores, as is essentially the case in Annelida, also hermaphrodite. Contrary to the behavior of oligochaete annelids which adhere in pairs, with anterior ends pointing in opposite directions, two Planaria maculata mate with heads in the same direction (Fig. i).. FIG. i. Attitude assumed by two Planaria •maculata during copulation. The anterior
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. COPULATION IN A TURBELLARIAN WORM. 299 or whether the spermatozoa may not be deposited in the atrial cavity of each worm and an exchange of them be effected by simple apposition of the pores, as is essentially the case in Annelida, also hermaphrodite. Contrary to the behavior of oligochaete annelids which adhere in pairs, with anterior ends pointing in opposite directions, two Planaria maculata mate with heads in the same direction (Fig. i).. FIG. i. Attitude assumed by two Planaria •maculata during copulation. The anterior ends are maintained side-by-side and flattened on the supporting substance (bottom of watch-glass in this case), oriented alike. About one third of their length posteriorly there begins a rather slight spiral twisting of the flat, oral surfaces of the worms against one another, so that the left ventral side of the right worm of a pair becomes lifted up against the right ventral side of the left worm. This twisting is carried further, posteriorly, so that the tail ends of the worms may even cross one another. At a point on the dorsal surface of each, opposite the external opening (genital pore) of the atrium, there was a marked depres- sion caused by the extension of the penis directly underneath. This indicates that the penis of each worm is drawn into the atrial cavity of the copulating mate by a definite muscular grasp on the part of the walls of the enveloping atrium. This is also suggested by the narrowing of the proximal end of the extended penis; this is evident in Fig. 2. The relation of the two copulants is thus presumably as in Fig. 2; this is purely a diagram, however, and one may not infer that the penes necessarily lie laterally to. 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 Biologi
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
