Ifli 



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t of Carnegie Inatitation 



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( 735 ) 



XIV. 



- On Intestinal Respiration in Annelids'; with Considerations on the Origin 

 and Evolution of the Vascular System in that Group. By J. Stephenson, 

 M.B., D.Sc. (Lend.), Major, Indian Medical Service, Professor of Biology, 

 Government College, Lahore. 



(MS. received August 29, 1912. Read March 17, 1913. Issued separately November 7, 1913.) 



CONTENTS. 



Oligoch^ta. 



1. The phenomena of aiitiperistalsis and 



ascending ciliary action in the 

 intestine of aquatic Oligoiha-la . 



Summary 



Exceptions to the general rule . 



On the possible descent of ( 'hxtoijaster 

 from parasitic ancestors 



2. The contractions of the alimentary wall 



in the aquatic Oligocluvta in 

 relation to those of the vascular 

 system 



736 

 744 

 745 



745 



748 



II. 



III. 



The investigations recorded in the present paper have been carried out at various 

 times during the last six years. A number of the observations on aquatic Oligocha^ta 

 were made some time ago in India, and, along with some of the theoretical conclusions, 

 formed Part IV. of a Thesis ("Studies on the Aquatic Oligochaeta of the Punjab") 

 presented in 1909 for the D.Sc. degree of the London University. This division of 

 the paper has been considerably extended as a result of further investigations on Indian 

 freshwater forms, and on the littoral OligochtBta of the Clyde, the latter carried out 

 at Millport in 1909. The portion of the present paper which is concerned with the 

 Polychjeta and smaller groups represents work done in 1909 at Millport, and in 1912, 

 during my occupancy of the London University table, at the Plymouth Laboratory. 



The observations on intestinal respiration in ( )ligoch8eta, especially those which 

 concern the relation of the antiperistaltic contractions of the gut to the contractions of 

 the dorsal vessel, led me, in conjunction with my investigations into the anatomy of 

 the circulatory system in these forms, to the views on the evolution of the vascular 

 system which are expressed in Section 3 of Part I. My original object in studying the 

 Polychajta was to find out whether the facts of anatomy and physiology in that group 

 supported these views. The observations which resulted, while in a general way con- 

 firmatory, add nothing to the argument ; and the consideration of the evolution of 

 the vascular system has therefore been left at the end of the part dealing with 

 Oligochajta, where it most naturally occurs. Certain phylogenetic speculations, on 



TRANS. ROV. SOC. KDIN,, VOL. XLIX. PART 111. (NO. 14). 101 



SMITHSONIAN INSTITUTION 

 WASHIII«TON 25. D.C. 



