. Zoology for high schools and colleges. Zoology. DEVELOPMENT OF GORAL POLYPS. 83 spermatic bodies rupture the walls of their respective glands situated on the fleshy partitions. As in Actinia, Lacaze- Duthiers thinks the fecundation of the egg occurs before it leaves the ovary, when also the segmentation of the yolk must take place. Unlike the embryo Actinia, the ciliated young of the coral, after remaining in the digestive cavity for three or four weeks, make their way out into the world through the tentacles. The appearance of the young, when first observed, was like that in Fig. 55, A, bei
. Zoology for high schools and colleges. Zoology. DEVELOPMENT OF GORAL POLYPS. 83 spermatic bodies rupture the walls of their respective glands situated on the fleshy partitions. As in Actinia, Lacaze- Duthiers thinks the fecundation of the egg occurs before it leaves the ovary, when also the segmentation of the yolk must take place. Unlike the embryo Actinia, the ciliated young of the coral, after remaining in the digestive cavity for three or four weeks, make their way out into the world through the tentacles. The appearance of the young, when first observed, was like that in Fig. 55, A, being an oval, ciliated gastrula with a small mouth and a digestive cavity. The gastrula changes into an actinoid polyp in from thirty to forty days in confinement, after exclusion from the parent, but in nature in a less time, and it probably does not usually leave the mother until ready to fix itself to the bottom. Before the embryo be- comes fixed and the tentacles arise, the lime destined to form the partitions begins to be deposited in the endq- derm. Fig. 55, C, shows the twelve rudimentary septa. These after the young polyp or " actinula" has become stationary, finally enlarge and become joined to the external walls of the coral now in course of formation (Fig. 55, C, c), forming a groundwork or pedestal on which the actinula rests. D represents the young polyp resting on the limestone pedestal. Lacaze-Duthiers found that the embryo polyp which had been swimming about in his jars for nearly a month, sud- denly^ within the space of three or four hours after a hot sirocco had been blowing for three days, assumed the form of small disks (Fig. 55, B), divided, as in the Actinia, into twelve small folds forming the bases of the partitions Fig 55 —Development of a coral polyp, Aslroicl'S calyculoris. A. ciliated gastrula; 3, young polyp with 12Fepta; G, D. young polyp farther advanced, with 12tentacles; c, the coralluEi and limestone septa begin- ning to form
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Keywords: ., bookcentury1800, bookdecade1880, bookpublishe, booksubjectzoology
