. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. Structure of the Oligocholia. 93 ment 12. The atrium commences as a sinuous tube, which widens out to form a large thin-walled sac with muscular walls. This sac when cut open (see fig. 1) is seen to be nearly. Sperm-duct of Phreodrilus. A, atrium ; /, its junctiou with vas deferens ; j, junction of the latter with ca^cal appendage (Sp); , vas deferens; p, external pore of atrium. The segments are numbered. rilled with a much coiled continuation of the atrium and the vas def
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. Structure of the Oligocholia. 93 ment 12. The atrium commences as a sinuous tube, which widens out to form a large thin-walled sac with muscular walls. This sac when cut open (see fig. 1) is seen to be nearly. Sperm-duct of Phreodrilus. A, atrium ; /, its junctiou with vas deferens ; j, junction of the latter with ca^cal appendage (Sp); , vas deferens; p, external pore of atrium. The segments are numbered. rilled with a much coiled continuation of the atrium and the vas deferens. The vas deferens makes its exit from the atrium at a point nearly opposite to its entrance ; just before this point it gives off (j in the figure) a diverticulum which, after being bent several times upon itself, ends blindly in the neighbourhood of the funnel in which the vas deferens ter- minates. The periatrial sac is filled with ripe spermatozoa not indicated in the woodcut. It is not, however, as far as I can ascertain, a ccelomic sac ; its cavity is simply produced by a splitting off of the greater part of its muscular tissue from the atrium. How the spermatozoa find their way in, unless it be through the gaps between the individual fibres, I cannot imagine; neither have I succeeded in finding any communication be- tween the sac and the interior of the vas deferens. The diverticulum of the vas deferens is lined with a non -ciliated glandular epithelium and has a muscular covering ; its struc- ture is indeed precisely that of the unusually elongated. 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 London, Taylor and Francis, Ltd
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