The most common example among fishes is that seen in the relationship 

 of the coeliac artery and the mesenteric artery . In some species (for 

 example the ribbon-fish /frichiurus haumela/ and the cod) these vessels 

 originate quite independently from zhe dorsal aorta, while in other species 

 (such as Thunnus orientalis and the deep-sea bass /Niphon spinosus/ ) they 

 are joined to form the coeliaco-mesenteric artery. Furthermore, the 

 positional relationships of the points of origin of this coeliaco-mesenteric 

 artery and of other arteries such as the subclavicular are remarkably 

 variable o In the deep-sea bass the coeliaco-mesenteric originates at a 

 point anterior to the subclavicular while in Thunnus and Auxis it originates 

 posterior to the subclavicular. 



According to Kishinouye's researches, in the genera Buthynnus and 

 Auxis the anterior and posterior subcutaneous arteries originate as two 

 separate vessels from the dorsal aorta, while in Katsuwonus they are not- 

 separate but form at first a single common vessel originating from the 

 dorsal aorta and then divide later into two vessels. Also according to 

 his descriptions and figures the points of origin of the subcutaneous 

 veins in one species of Thunnidae, the yellowfin tuna, are remarkably 

 variable. 



In view of what has been said above about the variability of blood 

 vessels it is not at all unreasonable to assume that in some individuals 

 of Gnathagnus elongatus the basal portions of the subcutaneous arteries 

 and the subclavicular arteries, which originate immediately anterior to 

 ■chem, may be fused together. If this assumption is allowed, it may be 

 said that the subcutaneous arteries of this species and of the Plecostei 

 are identical. And even supposing that the subcutaneous arteries in this 

 species are not homologous with those of the Plecostei, it goes without 

 saying that since the subclavicular artery is originally a kind of segmental 

 artery, the subcutaneous arteries of this species, which are branches of the 

 subclavicular, should also be classed as segmental arteries „ Accordingly 

 it should require no further argument to show chat the subcutaneous arteries 

 ^_in the Plecostej^j, which are just highly developed segmental arteries, 

 should be considered to belong to the same system. 



On the basis of the preceding arguments there is no obstacle, either 

 in Kishinouye's own views or from the point of view of comparative anatomy, 

 to saying that the subcutaneous vessels of the Plecostei and of the 

 Teleostei are in the broad sense identical. 



VI. Subcutaneous Vessels Are not Peculiar to the Plecogteio 



As explained above, the subcutaneous vessels of the Plecostei are 

 comparatively conspicuous developments of the segmental vessels of the 

 anterior portion of the body and are not in the least a new system 

 peculiar to the Plecostei. Furthermore, as shown above there are various 

 species of teleostean fishes which possess subcutaneous vessels developed 

 like those of the Plecostei, and therefore it goes without saying that 

 these vessels are not, as Kishinouye categorically affirmed, a peculiarity 

 of the Plecostei. 



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