400 PEOF. G. B. HOWES ON THE 



the supra-renal body in the Ichthyopsida {Bdellostoma) probably 

 represents a metamorpliosed excretory blastema. 



I trust to have shown in the foregoing that the appendix 

 digitiformis and its related conduit correspond, in fundamental 

 relationship, with the appendix vermiformis and caecum coli ; 

 and I think it not improbable that in the former, as represented 

 in the Batoidei {cf. ante, p. 398), we may be dealing with the 

 latter in their original form. It is a curious fact that Monro, in 

 his classical work on Pishes, referred to the appendix digitiformis 

 on one page (23. p. 84) as the " appendix vermiformis " and on 

 another (p. 92) as the " caecum ; " while Wiedersheim, com- 

 menting (33. p. 565) on the size and character of the csecum coli 

 of Ampliisbcdna *, has incidentally likened it to the appendix 

 digitiformis of the Selachii. I would go further, and openly 

 declare a belief in homology between the two sets of structures 

 as defined by myself (p. 394) until proof to the contrary, more 

 conclusive than that which is at present forthcoming t, shall 

 have been brought forward. 



IV. On the CcBCum of the Teleostei. 



It is customary in text-books to deny the existence of a caecum 

 among the Teleostean fishes. Such an organ was, however, 

 accorded them by Home in 1814 {Scorpcena [15. p. 389, 16. 

 pi. xcii.j) ; Rathke, ten years later, described $ a caecum in Cyclo- 

 pterus (" See Hase ") and Trigla lyra, while Cuvier and Valen- 

 ciennes accredited the same (5. p. 354) to Box in 1830. 



* On examiuation of this in Lepidosternon, Blamis, F achy calamus, and 

 Amfhisbcena (alha,fuIiginosa, and darwinii), I fail to see anything much in 

 advance of the oi'dinary Lacertilian type. 



1' The danger of drawing comparisons from the histological structure of the 

 alimentary mucous membrane alone is greatly increased by the discovery of 

 thickly set Payer's patches in the large intestine and rectum among Rodents, 

 Insectivores (Dobson, Journ. Anat. & Phys. vol. xviii. pp. 388-392, 1884), 

 and Apes {Hapalemur, Beddard, P. Z, S. 1884, p. 395). A similar caution 

 is necessitated by Weber's description of racemose sudoriferous glands in the 

 Hippopotamus (" Studien liber Saugethiere," Ein Beitrag zur Frage u. d. Ur- 

 spung d. Cetaceen, pp. 14-18, Jena, 1886). 



X 29. pp. 80, 81 . He also attributed to Polyptcrus a ctecum, with the com- 

 ment " wen ich mich richt erinuere." There can now be little doubt that Joh, 

 Miiller was right in subsequently regarding this (' Ban u. Grenzen der Ganoiden,' 

 p. 23) as a pyloric egecum; for, among Teleostei, the caeca pylori may be 

 reduced {Ammodytes, cf. Eathke, 29. p. 87) to a single representative. 



