. A manual of zoology. Zoology. 220 Ca-LENTERATA ... inf the rt'sopliagus, there may he others which do not reach the esophagus and liehinij;iiig to secondary, tertiary or other series (lig. 104). The septa support a numl)er of important organs: tire mesenterial hhimcnts, gonatls, and muscles. The iiwsciiteridl Jilaiiuiils are thick strands of epithelium, rich in glands and nettle cells, fastened like a hem on the edge of the septa. Since they are much longer than the peristomial- pedal length of the septa, they cause these latter to wrinkle and fold, thus strikingly resembling the mesenteiies
. A manual of zoology. Zoology. 220 Ca-LENTERATA ... inf the rt'sopliagus, there may he others which do not reach the esophagus and liehinij;iiig to secondary, tertiary or other series (lig. 104). The septa support a numl)er of important organs: tire mesenterial hhimcnts, gonatls, and muscles. The iiwsciiteridl Jilaiiuiils are thick strands of epithelium, rich in glands and nettle cells, fastened like a hem on the edge of the septa. Since they are much longer than the peristomial- pedal length of the septa, they cause these latter to wrinkle and fold, thus strikingly resembling the mesenteiies of the mammals. They en-\-elope the food and press it in, thus aiding the succeeding intracellular digestion. Lower down, in some species, the lilaments become free and form long tlireads, acoiilia, rich in nettle cells which are protruded for defence, either through the moutli or pores (cincliih's) in the column. The gonads âonly exceptionally hermaphroditic âlie bcsitle the mesenterial tlrreads as thickenings of the septum (lig. 192, g). The germ cells arise from the entoderm, but early migrate into tlie mesoglo-a of the septum (1Q3, 0). The eggs, when ripe, escapie into the gastrovascular cavity. The young leave the parent at various stages of development, sometimes as planukc (lig. 107, A), sometimes as young with tentacles. The muscles are â WM-y important, morphologically. Muscles anil nerves occur in lioth ectoderm and entoderm; but while the nerves are best developed in the ectoderm, especially around the mouth, and extend into the mesgolcea, the muscles of the ectoderm are weakly developed and are mostly confined to the peristome and the tentacles. The ento- dermal musculature is much stronger, just outside of the tentacles is usually a strong circular (sphincter) muscle (/») which can close in the top of the column o\-er the peristome. The septa also bear muscles, transverse on one side, longitudinal on the otlier, the hitter producing ridges on die septa (hg.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
