. The Bible and science. FtG. 163.—1. Egg of Hylodes martinicensis, twelve days old. lower surface;2. Young of Hylodes as it leaves the egg; c, tail. b. Adult male Hylodes,natural size. and that of a fern. The spore of the fern developsfirst into a prothallus, from which a plant resemblingthe parent arises, whereas in the lycopod the prothallusis developed in the spore itself, so that the plantresembling the parent springs at once from the spore. In figs. 104 and 165 w^e have diagrams representingthe development of an ascidian and of an amphioxus. MOLLUSC. Fjg. 164.—Development of an Ascidian.
. The Bible and science. FtG. 163.—1. Egg of Hylodes martinicensis, twelve days old. lower surface;2. Young of Hylodes as it leaves the egg; c, tail. b. Adult male Hylodes,natural size. and that of a fern. The spore of the fern developsfirst into a prothallus, from which a plant resemblingthe parent arises, whereas in the lycopod the prothallusis developed in the spore itself, so that the plantresembling the parent springs at once from the spore. In figs. 104 and 165 w^e have diagrams representingthe development of an ascidian and of an amphioxus. MOLLUSC. Fjg. 164.—Development of an Ascidian. a, the ovum, b and c, fissure of the ovum with enrlogenous formationof cells, ending in the formation of a spherical cellular mass. Inside this, fluid coll. cts so as to form abladder with cellular wall. Part of th-^ cell wall becomes inverted like the finger of a glove, andthis inversion forms the rudimentary intestinal canal. At this stage the embryo reminds us <if the(ioelenterata. e, Here the neural tube. S, the beginning of the spinal marrow,is being formed, itscavity still opens externally in front. Between it and the intestine (7), the chorda dorsalis (c). the axis ofthe inner skeleton has appeared. In the larvie of ascidians this rod passes along the tail which is castoff at a later .stage. There are some very small ascidians (appeiidicularia) which retain it through swim about by its means. VERTEBRATE
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectnaturalhistory, booky
