1 048 REPORT OF COMMISSIONER OF FISH AND FLSHEKIES. [68] 



bility to this interpretation ivS the circumstance that the tendons of the 

 inuscU\s which move the rays are attached, not to the " nodules " or 

 l)asihxr iiiterneural cartihi<;es, as stated by McMurrich, but to the mem- 

 brane of the bases of the rays envehjpinf;- these nodules. Such a con-" 

 tinuity of muscuhir and tendinous substance with the membrane of the 

 rays, iu wliieli ossific^atioii subsequently occurs, obviously points to the 

 conchisioii that all of these tissues arose from the same primitive blas- 

 teinn, /. e., the mesobhist. 



JSalfour ami I'arker* have i-eceutly ass«'rted that in the ventral limb 

 of the caudal of LvpUlosiena there are no interhtemal pieces develo])ed, 

 as there are in tlie dorsal side of the urostyle, ami that the rays which 

 lie below tlie canchil axis lie afj;ainst lia;mal pieces. They therefore urge 

 that the caiulal is n*)t serially homologous witli the anal or the dorsal. 

 Tliey also urge thai in Aiu/uilla, according to Huxley, while out- 

 wardly ther<' is an apparent serial homology of the dorsal and anal rays 

 over the end of the tail, such is not really the case, but that structurally 

 the tip of tin' (ail is truly hetorocercal, some rays resting directly upon 

 luemal i)ie<'es. In /'o///y>/rrj/.s- this is the <'ase, as well as iu most homo- 

 (!er<'al Teh'osts. though it is, ])erha]»s, unfair to urge this argument to 

 extremes, for, while the dorsal j)art of tJie caudal in Polypfents and 

 some Teleosts is undoubtedly serially honndogous with the dorsal, there 

 are eases auu)ng Xi'maUnfuathi and Scombeioids whei'e the interueural 

 ])ieces in this part of the caudal tin are supj)ressed. or so reduced and 

 co-ossitied as to be obscured. 



Xot only is this true, but there is also a certain amount of evidence 

 to show that some traces of interhaMnal ])ieces or their representatives 

 are present in tln^ tails of .Salmonoids as interspinous cartilages, or as 

 small nodules of cartilage at the ti])s of the luemal spines; that with 

 tlu^ advane«' of s])ee,iali/.ation sn]»pression of certain elements is not 

 oidy j)robable, but is ;dso. as we have seen above, su])i)orted by the facts 

 of the probable piesence of rudiments of interha^mal elements. Inter- 

 luemal elements are prol>ably developed about cartilage in mostTeleos- 

 tean forms, (certainly in sonw, and in a few forms they never develop 

 much beyoiul a eartilaginous condition, as in GustroHtomuH^ for example. 

 Why interh;emal or iiiterneural pi<'ees should apjiarently not be pres- 

 ent iu the caudal is not any more dillieult to understand than that the 

 basipterygium is reduced, and the rays niore nearly sessile in the Teleosts 

 than in most of the other members of the piscine series. In Gastrosto- 

 mufi, for examjile, a specialization of the jiectoral has been reached, as 

 a consequence of Mhich the rays are sessile upon the coraco-scapular 

 plate of cartilage, so that a condition is liere preserved which is transi- 

 tory in tish larva^. In all these cases snppiession of the intermediary 

 pieces has evidently occurred as g«meral specialization has proceeded. 

 li we regard (Jeyatodus as exhibiting the most jirimiti^e type of caudal ; 

 if it lias not, in fact, been atiected by a general tendency fo exhibit a 



Qn tlje {leyelopijjeut; of. Lcpi^gsteus, Philos, f raijs., 359-442, 1882, pis, 21-21.); 



