. Biological lectures delivered at the Marine Biological Laboratory of Wood's Holl [sic]. Biology. CLEAVAGE IN ANNELIDS. 105. Fig. Podarke, forty-two hours; prob., problematic bodies. From their staining reactions I infer that in Podarke, as in Nereis, these organs have a glandular function. A ventral band of cilia is present, but I have not been able to discover any paratroch. The enteron has grown and expanded so as to completely ob- literate the body cavity. Owing to the slow develop- ment of muscular tissue on the dor- sal surface of the larva, the body wall is composed of two very th
. Biological lectures delivered at the Marine Biological Laboratory of Wood's Holl [sic]. Biology. CLEAVAGE IN ANNELIDS. 105. Fig. Podarke, forty-two hours; prob., problematic bodies. From their staining reactions I infer that in Podarke, as in Nereis, these organs have a glandular function. A ventral band of cilia is present, but I have not been able to discover any paratroch. The enteron has grown and expanded so as to completely ob- literate the body cavity. Owing to the slow develop- ment of muscular tissue on the dor- sal surface of the larva, the body wall is composed of two very thin layers, ectoderm and endoderm, while the body wall on the ventral side is much thicker, and the amount of mesodermal tissue is evidently much greater. At present I am unable to state just what are the relations of the meso- dermal portion of the larva of this age, but an investigation now in progress will undoubtedly clear them up. Certain it is that the amount of definite mesoderm is very small when compared with such a form as Amphitrite, for in an earlier stage of approximately twenty hours, when Amphitrite has already begun to elongate and the germ bands are composed of "a great many " cells (Mead does not state how many), Podarke has no more than two mesoblast cells on a side. The young larva is very muscular, undergoing all sorts of distortions when irritated; but this activity is produced by the larval mesoblast cells de- rived from ^d, Jc, and Ja. These cells wander apart from one another, elongate, and form the larval musculature. As said before, I am not yet sure about the relations between these two sorts of mesoderm and the other body layers during the later larval stages ; but I believe that it will be found that by far the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Bio
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