INTESTINAL RESPIRATION IN ANNELIDS. 745 



Exceptions to the General Rule. 



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

 Oligochajta exhibit in general the phenomena of antiperistalsis and ascending ciliary 

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

 show antiperistalsis ; all except the Enchytrttidse, Branchiura sowerhyi, and the genus 

 Cha'togaster, show ascending ciliary action. 



Branchmra soivevhyi is one of the few Oligochseta wliicli possess gills. It is true 

 that certain NaididsB [Dero, Aulopho7-us, Brand liodrilus) have, in addition to branchial 

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

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

 absence of intestinal respiration. 



With regard to the Enchytra^idte it is to be observed that, thougli 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 Enchytraeus) with a net 

 when exploring the aquatic vegetation of tanks at Lahore ; but Enchytrasids 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 

 Enchytrfeids on one occasion only; in other cases numbers varying from 4 to G15 

 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 Enchytrteids, 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 Chwtogaster remains to be considered. This is perhaps the most remark- 

 able genus of the Naidid* ; and Ve.jdovsky (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 Naididoe 

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



