INTESTINAL CANAL OE THE ICHTHTOPSIDA. 401 



The terminal portion of tlie intestine in these fishes exhibits, 

 as a general rule, an increase in calibre and distensibility over 

 the rest, and at its point of differentiation there is usually- 

 present, in the adult, a well-defined valve (c/. Cuvier and Valen- 

 ciennes, 4. p. 502) which clearly suggests the ileo-colic valve * 

 of the higher Vertebrata. 



The csecal diverticulum, when present, overhangs this ; and? 

 although it never attains a considerable development, comparison 

 with the other Ichthyopsida and the Eeptilia leaves little room 

 for doubting that it represents those derivatives of the gut which 

 I have attempted to homologize in the preceding part of this 

 paper. Having accumulated some notes upon the same in those 

 genera before referred to which I have been able to examine, I 

 here tender them for what they may be worth. 



Triyla gurnardus. The ileo-colic valve is, in the adult, exceed- 

 ingly well marked — so much so that it reduces the ileo-colic 

 aperture to a minute perforation. The large intestine exhibits 

 but a small increase in calibre as compared with the ileum; and 

 there is consequently no trace, in the adult of this species, of an 

 overhanging lobe or caecum. I have observed, however, in a 

 young specimen of 16g centim. in length, a perceptible enlargement 

 of the antero- dorsal extremity of this viscus, suggestive of the 

 small caecum of the Frog {dv , fig. 3). 



Cyclopterus Imnpus. I am unable to confirm Eathke's state- 

 ment concerning the presence of a caecum in the adult of this 

 species. The ileum enters the large intestine antero-ventrally 

 {cf. PI. II. fig. 17) ; the increase in calibre of the latter is well 

 marked, and there is developed a highly efficient and flap-like ileo- 

 colic valve. In the young animal, however, the conditions may be 

 otherwise. I have examined two juveniles of this species f. 

 The intestine appeared, in them, Avhen looked at externally, to be 

 destitute of a caecum ; when opened from the side, care being 

 taken to avoid unnecessary displacement of the gut, the ileo- 

 colic aperture was seen to be situated ventrally (fig. 17) and, in 

 one of the two, comparatively far back. The ileo-colic valve 



* It is yery regrettable that this should be so frequently referred to, alike in 

 original monographs and text-books of both anatomy and physiology, as the 

 ileo-C£ecal valve. Huxley has long since shown this term to be expressive of an 

 error of observation in fundamentals (see Parker, P. Z. S. 1881, p. 62.5). 



1- Thanks to Prof. W. Mcintosh, F.E.S., and my pupil Mr. E. W. L. Holt. 



