108 DR. J. Sl'EPHKXSON ON THE MORPHOLOGY, CLASSIFICATION, 



described in the same way as in E. ashworthi ; it follows there- 

 fore that if E. ashworthi is similar to Trigaster, the majority of 

 species of Eiulichog aster, so far as known, are not. Speaking- 

 very broadly, there is indeed some similarity between all these 

 six species of Eudichogaster and Trigaster lankesteri ; in all, a 

 certain number of the micronephridia are of large size, much 

 lai'ger than in Pheretima, for example, or Eatyph<x.us, to take two 

 well-kaowu micronephridial genera. But this feature occurs also 

 in some species of OctoGhmtxis^-iw exactly those thi-ee species 

 previously referred to ; in these there are seven, three, or even 

 apparently only oiie nephridium on each side in each segment, 

 which make up in size what they lack in number. The m;i,jority 

 of species of Eudichogaster, in fact, approach in their nephridial 

 condition somewhat more closely to such forms as Octochcettis 

 pallidios and 0. 2}ccchpaharensis than to Trigaster lankesteri *. 



I am, however, not inclined to attach very great weight to 

 any argument from the nephridia. The possession of a certnin 

 number of microiiephrirlia of fairly large size does not necessarily 

 show genetic relationship ; it occurs, for example, in species of 

 Megascolides and Megascolex, which belong to a difierent sub- 

 family, the Megascoleciufe. Indeed there are very diverse 

 conditions within these two genera themselves. 



I think the above considerations show that the passage f)-om 

 OctochcBtus to Eudichogaster is just as easy morphologically as 

 that from Trigaster, and that thei'C is no difficulty in deriving 

 Eudichogaster from an Octochcetus ancestor which had the 

 characters of the group pallidus, pachpaha?^ensis, and hishambari. 



But if the morphological evidence is equally balanced, the 

 geographical evidence is strongly on the side of the descent of 

 Eudichogaster from Octocha'Mis. Octochcntus is a characteristic 

 Indian genus, found throughout the la.nd ; Eudichogaster is 

 exclusively Indian, and is found in a broad belt across the middle 



* In Eudichogaster ashtvorthi, towards tlie liindev end of the body the innermost 

 of the transverse series of micronephridia enlarges so as to resemble a mega- 

 nephridinm; the number of micronephridia in each segment appears to be small, — 

 in var. Mnneari it is about six on each side. In E. prashadi much the same 

 occurs, — there are about five on each side, regularly arranged behind each other in 

 succeeding segments till towards the hinder end, where the innermost becomes 

 larger and the others smaller, less regular, and more numerous. In E. barodensU 

 the three most dorsally situated micronephridia on each side of each segment are 

 larger than the rest, while at the hinder end the innermost (most ventral) also 

 enlarges. In E. bengalensix there are two pairs of large nephridia per segment in 

 addition to a number of small micronephridia; towards the hinder end the inner of 

 the two larger nephridia becomes more conspicuous than the other. In E. ehittn- 

 gongensis there are three or four nephridia on each side in each segment, arranged 

 "behind each other in succeeding segments, the outermost in each transverse row 

 being the longest; near the hinder end the innermost increases in size and becomes 

 more conspicuous. In E. trichochcettis there are four longitudinal rows on each 

 side of the body, but here the innermost series is the smallest. In E. parvus, 

 though the nephridia are " ditt'use," they are of considerable size. 



In Octochcetus pallidus the micronephridia in the post-clitellar segments are 

 about seven on each side in each segment, and they increase in size from the 

 ventralmost to the fifth, the two most dorsal being smaller again ; this difference in 

 size disappears towards the hinder end. In O. pachpaharensis X\\ev£, are three on 

 each side per segment behind the genital region, and in front even fewer. 



