. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 643 The epithelial cells lining the original (anterior) vesicle increase in height with the growth of the organ, while the cells lining the secondary (posterior) vesicle become thinner and thinner as it grows backward. The extreme of this differentiation is reached in a larva of about 16 mm. in length,- which is approximately the size of a young toadfish about to break away from its attachment. A sagittal section of the swim-bladder of such a larva is shown in Fig. 9. At this stage, the posterior chamber is lined with flat ep
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 643 The epithelial cells lining the original (anterior) vesicle increase in height with the growth of the organ, while the cells lining the secondary (posterior) vesicle become thinner and thinner as it grows backward. The extreme of this differentiation is reached in a larva of about 16 mm. in length,- which is approximately the size of a young toadfish about to break away from its attachment. A sagittal section of the swim-bladder of such a larva is shown in Fig. 9. At this stage, the posterior chamber is lined with flat epithelium; the anterior chamber contains only a slight cavity and is lined on all sides with a layer of. Fig. 9. Sagittal section of swim-bladder in 16 mm larva of Opsanus tau. anterior chamber, cp capillary bundles, cnt outer connective tissue layer of swim- bladder, epi epithelium lining the anterior chamber of the swim-bladder, mb lateral band of striated muscle, posterior chamber. X 125. very tall columnar cells; ventral to the tube connecting the two chambers is a conspicuous whorl of capillaries from which is to be formed the blood supply of the red gland. Soon after this stage, the larva absorbs the yolk-sac, breaks away from its attachment, and begins its free-swimming existence. Appar- ently coincident with this process, the swim-bladder becomes functional, or at any rate it assumes the structural relations of the adult organ. The cavity enlarges greatly, either as a result of, or as an ad- justment to, the secretion of gas; the tall columnar cells lining that portion of the anterior chamber just in front of the passage to the posterior chamber remain as a single layer of columnar epithelium and form the fundament of the red gland; all the remainder of the lining cells become transformed into flat epithelium. I have not yet studied this process in detail, but its careful investigation might add much to our knowledge of the swim-bladder, since this transfo
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