VII.. Summary and Cone. 



When Kishinouye in 191? in .olume 2 of the Suisan Gakkai Ho first 

 introduced the new Order of Plecostei, he gave as its primary characteristic 

 the presence of subcutaneous blood vessels and as its secondary character- 

 istic the position close to the spinal column of lateral areas of dark red 

 tissue with vascular plexuses.. In 1923 in Volume 8 P Number 3, of the 

 Journal of the College of Agriculture of the Tokyo Imperial Jniversity he 

 added as another secondary characteristic the development of vascular 

 plexuses within the body cavit . 



Kishinouye decided that these features of the Plecostei could be 

 considered of equal weight with the differences between the other Orders 

 of the Teleostomi, such as the Crossopterygii, Chcndrostei, Holostei, 

 and Teleostei, separated the Plecostei completely from the Teleostei as 

 then constituted, and set them up as a new Order Now that ; is sub- 

 cutaneous vessels,, which are the principal characteristic of this Order, 

 have been discovered in various teleosts and have been clearly proven not 

 to be peculiar to the Plecostei;, the latter have lost the main reason for 

 their status as a distinct Order ■> Consequently the point has been reached 

 where this Order should be abandoned Jiow that the main characteristic 

 has been los" i ; : -will naturally be completely impossible to maintain the 

 continued existence of the Order solely on the basis of the secondary 

 characteristics It is probably unnecessary to say any more about the 

 matter,, but I would like to point out as a preliminary to any discussion 

 that the presence of vascular plexuses in the dark lateral tissue and the 

 position of this tissue close to the spinal column as described by Kishinouye 

 can also be seen in the broadbill swordfish,, a teleostean species,, and are 

 not in the least peculiar to the Plecostei <, The positional relationship 

 between the spinal column and the dark lateral tissue is particularly 

 subject to striking variations in the sharks „ As for the vascular plexuses 

 in the body cavities of the Plecostei, circumstances have prevented my 

 having as yet had an opportunity to ascertain by an examination of many 

 species of teleostean fishes whether or not such plexuses occur also in 

 teleosts, and consequently I cannot at the moment decide this question, 

 but there is room for doubt as to their not occurring in any species of 

 the Teleostei,, However, even assuming that these vascular plexuses are 

 not to be found in any teleost and that they a re peculiar to the Plecostei, 

 it cannot be said that this single feature should be considered a character 

 equal in weight to those which differentiate the other Orders of the 

 Teleostomi If this single feature has a value great enough to separate 

 the Plecostei from the Teleostei as hitherto constituted, then what of 

 the tfeberian apparatus of the cyprinids? 



If the person who established this Order wishes to insist upon its 

 continued existence for the reason that these vascular plexuses have not 

 yet been discovered in teleostean species, then he must explain in detail 

 why it is that special organs like those of the cyprinids referred to above 

 do not have sufficient value to set that group of fishes apart from the 

 teleosts as a new Order while only these vascular plexuses , which belong 

 to the highly variable vascular system,, do have such value „ If such an 

 explanation cannot be given oi e explanation is unreasonable,, then the 



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