INTESTINAL RESPIRATION IN ANNELIDS. 745 



Exceptions to the General Rule. 



On a perusal of the foregoing table it will be seen that a number of the lower 

 Oligochseta exhibit in general the phenomena of antiperistalsis and ascending ciliary 

 action in the intestine. All the species observed, except those of the genus Chastogaster, 

 show antiperistalsis ; all except the Enchytrseidse, Branchiura sowerbyi, and the genus 

 Chwtogaster, show ascending ciliary action. 



Branchiura soiverhyi is one of the few Oligochaeta which possess gills. It is true 

 that certain Naididse [Dero, Aulophorus, Branchiodrilus) have, in addition to branchial 

 respiration, an ascending ciliary current in the intestine. Still, it seems not improbable 

 that in Branchiura sowerbyi the presence of branchial may be correlated with the 

 absence of intestinal respiration. 



With regard to the Enchytrseidse it is to be observed that, though included in the 

 present investigation for reasons which will appear more fully in the next section, they 

 are by no means strictly, or even predominantly, of aquatic habit. I have only twice 

 obtained single immature specimens (probably of a species of Enchytrseus) with a net 

 when exploring the aquatic vegetation of tanks at Lahore ; but Enchytrseids are to be 

 found in profusion, for example (at least in Europe), under stones along the seashore, 

 on both sides of the upper tide limit ; or under stones that have been lying for some 

 time undisturbed almost anywhere ; or in moist ground. Some are plant parasites ; 

 others are found in dung-heaps. They cannot live in absolutely dry ground ; but the 

 immense numbers that exist in the soil may be illustrated by some figures given by 

 Bretscher (10). This observer found a sample of earth to be entirely devoid of 

 Enchytrseids on one occasion only; in other cases numbers varying from 4 to 615 

 were found in about two square decimeters of ground. 



The phenomenon of ascending ciliary action can only be of use for respiratory 

 purposes where the animal lives in water ; and since this is not the case with the 

 majority of Enchytrseids, and perhaps was not the case with the ancestor of the family, 

 it is not to be expected that it should occur amongst the existing members of the 

 group. The ascending peristalsis, as has already been noted, and as will be further 

 shown in the next section, subserves the circulation ; and hence, though its original 

 import, according to the view here taken, was probably respiratory or alimentary, it 

 has been retained, and is found regularly throughout the group. 



On the possible Descent of Chsetogaster from Parasitic Ancestors. 



The case of Chsetogaster remains to be considered. This is perhaps the most remark- 

 able genus of the Naididae ; and Vejdovsky (54) separates it as a distinct family. 

 Later writers have not followed this example ; but whether or not the characters of 

 the genus are deemed sufficiently distinctive to justify this course, it must be admitted 

 that the Naididse are its nearest relatives. Now the other genera of the Naididse 

 appear, so far as yet observed, to show regularly both of the phenomena here under 



