404 PROP. G-. B. HOWES OlS" THE 



In view of the constancy of this valve, and of its relationships 

 previously referred to, as compared with the variability of the 

 annular folds, I am decidedly of opinion that, if the homology be- 

 tween the latter in the Smelt and Salmonidse named be admitted, 

 that segment of the gut which bears them must represent some- 

 thing more than the large intestine, as I have defined it — where- 

 upon the post-valvular portion of the Smelt's intestine and the 

 annulated segment of that of the Salmon and Trout would appear 

 to be non-homologous. In face of these facts and considerations, 

 the conditions in Ohirocentrus become most perplexing. On 

 comparison with the Elasmobranchs, its valved intestine might 

 repre'sent that which I regard, in them, as the small intestine — 

 in which case the large intestine would appear to be absent and 

 the gut, taken as a whole, to be less modified than that of even 

 the Granoids. On the other hand, comparison with the Salmon 

 would appear to show (if the annulated segment of the gut of 

 that fish should have the value which Eathke attached to it) that 

 the valved gut in Ghirocentrus might represent the large intestine 

 as defined by myself. 



That, in seeking to establish homologies, too much importance 

 must not be attached to the mere presence or absence of an 

 intestinal spiral valve in the Teleostei, is clear, from the differ- 

 entiation of a like structure in the oesophagus of Chanos *, and 

 of an essentially similar one in that of the IfarsipohrancMi f. I 

 have attempted to show (ante, p. 395) that the large intestine is, 

 in the Plagiostomes, well marked though short. The appendix 

 digitiformis is smallest where situated furthest back ; and in the 

 young of those forms which I have been able to examine {Scyl- 

 Uum, Mustelus, Acanthias, Septandms) it is situated further 

 forwards than in the adult. We have thus a suggestion of 

 reduction proportionate to a shortening up of that which I 

 regard as the large intestine ; a further extension of such a 

 process (be it at work) would give us the condition met with in 

 the Granoids and Ghirocentrus (supposing the resemblances 

 between the intestine of this fish and that of the Plagiostomes to 



* Cuvier and Valenciennes (6. p. 185). 



t G-imther describes this (' Introduction to the Study of Fishes,' p. 128) as 

 consisting of "numerous longitudinal folds." They are oblique and more 

 nearly ovoidal. Parker has shown (26) that the particular characters in the 

 "pitch" and mode ofdisposition of such " valves" are matters of no morpho- 

 logical significance {cf. his pi. 10. figs. 1 and 4, andpl. 11. figs. 6 and 8).' 



