we vONeA NEW SPECIES Ob eae AN € HILO- 
PRILUSs AND “CERTAIN OFFER Ree OuUAT TEC 
OELGOCHAE TA. WITH REMARKS. ON 
Ch PEARL PZALT LON: LN dee NVA Dinas. 
By J. StepHenson, M.B., D.Sc. (Lond.), Major, I.M.S., 
Professor of Biology, Government College, Lahore. 
(Plates xi—xii.) 
I received in November I91tr a tube of small aquatic Oligo- 
chaeta, sent to the Indian Museum from Madras by Prof. K. 
Ramunni Menon. The tube contained eight specimens, of which 
however one was a fragment incomplete at both ends. In one 
case the animal was in process of dividing asexually ; none 
possessed sexual organs. 
The worm belongs to the group of gilled Oligochaetes, and 
is closely related to the two Naids described, one by Bourne (4) 
under the name of Chaetobranchus sempeni from Madras, and one by 
myself (15) as Lahoria hortensis from Wahore. Since gilled 
Oligochaeta are interesting on account of their rarity, and 
since the present form gives occasion for some remarks on 
the ‘‘ cephalization’’ of the Naididae, I describe it here as far as 
possible in detail, My remarks go under four heads :—(I) 
Anatomy, (2) Asexual reproduction, (3) Systematic position, (4) 
Cephalization in the Naididae. It is to be remembered that I 
have only had the opportunity of examining preserved specimens. 
: (x) Anatomy. 
In length the worms were from 8 to 15 mm.; they were 
brownish in colour; the two longest consisted each of 130 
segments, plus a number of minute and scarcely differentiated 
segments in process of formation at the posterior end; another 
specimen had 77 segments with again a similar region of newly 
forming segments posteriorly. The gills were in most specimens 
just visible to the naked eye as processes on the anterior portion 
of the body. The prostomium was short and rounded. Succeeding 
the mouth was a short prebranchial region, which will be considered 
more fully below. 
Gills.—The gills are elongated hollow evaginations of the 
body-wall; as in the related forms mentioned above, they contain 
a vascular loop, and, in the anterior portion of the body, the 
capillary dorsal setae also. Since they correspond in position with 
the dorsal setal bundles, they form a dorso-lateral series on 
each side. ‘They diminish in size posteriorly, and the long dorsal 
setae are then no longer enclosed in them. 
