. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. 620 Bashford Dean Tviemorml Volume culation as shown in Dean's drawings Pigures 7 and 8, plate I . The reader can then compare the two statements and detect the errors. Circulation on Dorsal Surface of Yolk Sac.—As explained above, Dean had Nishi- ka-w,-a"s figures redra^^^ii for reproduction by lithography. It may be seen in the Kne cut TText'figure 41 and in the copy fTigure 7- plate I that the 43'mm. fish has considerable freedom of movement on its yolk sac, as is shov^-n in the position of the artery under the tail
. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. 620 Bashford Dean Tviemorml Volume culation as shown in Dean's drawings Pigures 7 and 8, plate I . The reader can then compare the two statements and detect the errors. Circulation on Dorsal Surface of Yolk Sac.—As explained above, Dean had Nishi- ka-w,-a"s figures redra^^^ii for reproduction by lithography. It may be seen in the Kne cut TText'figure 41 and in the copy fTigure 7- plate I that the 43'mm. fish has considerable freedom of movement on its yolk sac, as is shov^-n in the position of the artery under the tail of the reversed embryo. This arter>^ is unlike that of the 39'mm. embryo Figure 50, plate V) in that it gives off on the left side one small quickly bifurcating branch, but is Hke the former in that the main arter>^ divides into two just where it passes over the equator of the yolk mass. The venous system on the embryonic side of this egg shows much grovvth and differentiation over that of the 39'mm. embryo portrayed in Figure 50, plate \'". In the hinder and lower segment of this half of the yolk, the dendritic arrange- ment of the venous system shows about as in the 39'mm. embr>'o. But in the region just posterior to the yolk stalk, large veins on each side empty into the main Test-ngure 31 The egg oi Acanthias vulgaris in its ci55. This is the earliest figure found portrajong the embryo and its viteUine circulatory system. For explanation see caption to Text-figure 30. After Lev%, 1852, Fig. 6, pL m. The oldest figure known to me portraying the circulatory system of a shark • Acan- thias vulgar\s=Squalus acanthias^ is that by Leydig '1852, Fig. 67, pi. Ill shown in my Text-figure 31. Here the viteUine artery branches at the edge oi the blastoderm and forms the arterial ring -his "sinus terminaHs"'), which gives off many branches behind. These communicate with the developing venous system whose main trunk enters the yolk stalk from
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