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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 4 1 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 trunk. 



Test-ngure 31 

 The egg oi Acanthias vulgaris in its horr.y 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 the rear. This figure portrays a circulation intermediate between that of 

 Dean's 39' and 43'mm. embryos. 



Circulation on Ventral Surface of Yolk. — The blood-vascular system on the ventral 

 (lower) side of the egg carrying the 43'mm. embryo will now be considered. It is un- 

 fortunate that there is not at hand at least one figure 5ho\<.-ing in an earlier stage the 

 development in Chlamydoselachus of the yolk'\-ascular system on this side of the egg. As 

 shown in Figure 8, plate I, the bifurcating viteUine artery, just below the equator of the 

 egg, has formed the arterial ring, which shows a number of striking irregularities. The 



