. Contributions to the natural history of the United States of America. Zoology; Chelonia (Genus); Ctenophora; Cnidaria; Animals. Chap. I. REPRODUCTION OF CORYNE MIRABILIS. 195. of its component layers (wood-cut 13). The outer wall {l>), embracing the whole medusa-bud, bends upon itself (i^), at the edge (a"^) of the cup of the inner wall (a), and, following the inner surface of the latter, there be- coming the innermost of the three walls of wdiich the um- brella is composed in the newly freed medusa, passes to and over the proboscis («'), where it constitutes the outer wall. In this
. Contributions to the natural history of the United States of America. Zoology; Chelonia (Genus); Ctenophora; Cnidaria; Animals. Chap. I. REPRODUCTION OF CORYNE MIRABILIS. 195. of its component layers (wood-cut 13). The outer wall {l>), embracing the whole medusa-bud, bends upon itself (i^), at the edge (a"^) of the cup of the inner wall (a), and, following the inner surface of the latter, there be- coming the innermost of the three walls of wdiich the um- brella is composed in the newly freed medusa, passes to and over the proboscis («'), where it constitutes the outer wall. In this way, the cup-like disk of the medusa becomes triple- walled (f) a b^), and the proboscis double-walled {u n^). If we include the radiating tubes in a section, the inner wall being doubled by having a channel hollowed in its thick- ness, then the disk appears quadruple-walled (PI. XVIII. Fiff. 9, b a a' c), and may be mistaken as having really four walls, unless carefully examined in all its relations. Other parts of the organism have also developed new features; the radiating tubes have broadened considerably, especially at two points (PI. XVIII. Fiff. 9, I) of each, half way between the base and extremity, so that the channels of neighboring tubes are diverted laterally into broad sinuses. Of course this will be understood to be a hollowing in the thickness of the middle wall. As the me- dusa grows larger and older, these sinuses become narrower and deeper (PI. XVIII. F/ff. 10, and wood-cut 14, I), and con- sequently each one approaches its neighbor. What appear to be intervening walls, both in the last stage (PI. XVIII. F/'ffS. 9, l>^ I c) and in this {F/ff. 10 and wood-cut 14, l>^ I e), thi'ough Avhich the approximating sinuses would appear to be forcing their way, are profiles of an oblic^ue view of the innermost wall, seen at a deeper focus.^ That portion beyond the approximating sinuses, and the outer end of the disk (PL XVIII. Fiff. 10, and wood-cut 14, b^), is de
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