49 J 



V. On the Intestinal Spiral Valve in the genus Eaia. By T. Jeffery Paekee, B.Sc, 

 Assoc. B.S.M., Lecturer on Biology in Bedford College, London, and Demonstrator 

 in the Boyal School of 2Iines. [Comimtnicatcd by Prof. T. H. Huxley, F.E.S.) 



Keceived November 7th, 1879. — Read December 16th, 1879. 



[Plates X. & XI.] 



CojJ TENTS. 



1. Introductory § 1 



2. Method of examination § 2 



3. Generic description of intestine of Rata . . § 3 



4. Table of constant and inconstant features 



in spiral valve of liaia § 4 



5. Detailed description of spiral valve of Raia 



§§ 5, 6, & 8 



6. Definition of the four types of spiral valve § 7 



7. Variations in absorbing surface of spiral 



valve §§9 & 10 



8. Obstruction to passage of food offered by 



the various forms of valve § 11 



9. Character of mucous membrane of spiral 



valve § 12 



10. Concluding remarks on spiral valve of 



Raia § 13 



11. Spiral valve of Sci/lUum § 14 



12. „ „ „ Notiilanus § 15 



13. ,, ,, „ Cestracion § 16 



14. „ „ „ Chimaira § 17 



15. Scroll valve of Zyrjmia § 18 



16. Spiral valve of Lepidosiren and Cera- 



todus § 19 



17. Spiral valve of Petromyzon § 20 



18. Concluding remarks, and table showing 



relations of spiral and scroll valves §§ 21 & 22 



I have not judged it necessary to give a special abstract of the paper, as aU the results of my observations 

 are to be found in a condensed form in §§ 4, 6, 10, 13, and 21. 



§ 1 . FoE) the last few years I have had the opportunity of examining a large number 

 of intestines of various species oi Eaia, and have been greatly struck with the astonish- 

 ing amount of variability exhibited by the spiral valve — a variability most surprising 

 when one considers the great physiological importance of the structure in question, 

 and the extent of the probable lapse of time since it first came into existence. 



The best accounts of the spiral valve are to be found in the works of Claude 

 Perrault \ Miiller ^ and Dumeril ', the two latter giving a general description of the 

 valve, with the main differences it presents in the chief genera of Elasmobranchs, while 

 Perrault has an excellent figure and description of the very typical form of valve dis- 

 covered by him in the " Renard mariu." I have been able to find none but the most 

 general description of the valve of Baia ; and the only figure of it I have met with is 

 that in Monro's ' Structure and Physiology of Fishes,' where, being drawn in its flabby 

 fresh condition, it is impossible to get any correct idea of its form and relations. 



' ' Mem. pour servir a I'hist. nat. des Animaux,' 1G71. (Kepublishcd 1736.) 

 '' Anatomie der Myxinoiden. ' Ichthyologie Generale. 



