. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. NEPHRIDIA OF NEREIS LIMNICOLA 369 The canal has an overall length of 2232 micra and a mean diameter of micra (the length of the canal of the smallest nephridium was found to he 1800 micra and its mean diameter was micra). There appear to he four different regions with respect to lumen diameter. The first, diameter about 24 to 30 micra, extends from the entrance of the post-septal canal for about 800 micra; the second, whose diameter is in the range of 36 to 40 micra, extends for another 600 micra; the third, the na
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. NEPHRIDIA OF NEREIS LIMNICOLA 369 The canal has an overall length of 2232 micra and a mean diameter of micra (the length of the canal of the smallest nephridium was found to he 1800 micra and its mean diameter was micra). There appear to he four different regions with respect to lumen diameter. The first, diameter about 24 to 30 micra, extends from the entrance of the post-septal canal for about 800 micra; the second, whose diameter is in the range of 36 to 40 micra, extends for another 600 micra; the third, the narrowest part, about 12 to 27 micra, runs for approximately 200 micra before grading into the final portion; the last portion, about 750 micra in length, increases from 27 to 48 micra, then decreases somewhat irregularly until it reaches the nephridiopore, where its diameter is 6 micra. The sudden widening of the canal just prior to the nephridiopore gives the appearance of an ampulla. In the last portion of the nephridial canal, as the nephridiopore is approached, the wall of the lumen seems to become thicker and more dense. Closer inspection shows that the network of the interstitial tissue has become more concentrated in the immediate area of the canal and that there seems to be an increase in the number. FIGURE 10. Graphic representation of the inner diameter and wall thickness of a nephridial canal of Nereis liinuicola from up-river (reconstructed from sectioned material). PSC, post- septal canal; NPR, nephridiopore. of granular inclusions contained in this net. There are large nuclei scattered through the wall of the canal, until, at a point about 40 micra from the external opening, a more regular distribution is assumed, with three or four nuclei apparently in the same plane. This continues to the last 8 micra, where large nuclei are clustered around the canal, and the wall loses its identity in the surrounding tissue. As was the case in N. ve.\~illosa, there is no ciliat
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
