286 DR J. STEPHENSON ON 
being the absence in Lahoria of gills and dorsal setee on the segments from the second — 
to the fifth, and their presence on these segments in Chetobranchus. It is thus note- — 
worthy that the coexistence of Branchiwra sowerbyi and Chetobranchus in artificial 
surroundings in England should be paralleled by the coexistence of Branchiura 
sowerbyt and Lahoria under natural conditions in India. 
The pond in which the worms were found was one of a series occurring in a small 
nullah on the outskirts of Lahore. The surface drainage of the jail runs into this 
nullah, so that, unlike most small ponds in this neighbourhood, it is probably seldom 
altogether dry. At times, e.g. after rain, there is a continuous stream of water along 
the nullah. 
Methods.—The best method for the observation of the living animals is the employ- 
ment of the binocular microscope with comparatively low powers; this is the easiest 
way of obtaining a conception of the complicated relationships of the blood-vessels, and 
the mode of their contraction. 
The setz are best studied by killing the animals by a narcotic (methyl alcohol, 
chloretone) and leaving them in the water for a few hours till they become soft and are 
just beginning to disintegrate. A worm is then carefully placed on a slide in glycerin 
and the coverglass lowered; the weight of the coverglass is sufficient to cause a 
specimen in this condition to flatten out completely, and the sete, retaining their 
arrangement, can then be viewed in one plane. 
Parts of the genital system, and especially the chitinous penis sheath of the 
Limnodrilus, can be isolated by teasing under the binocular microscope. 
Serial sections (5-10“) were stained with Heidenhain’s iron-hematoxylin followed 
by eosin, and with Delafield’s heematoxylin. ; 
Branchiura sowerbyi Bedd. 
Since the original discovery of this worm by Bepparp it has been recorded by L.. 
PrrRter (8), who has found it in different years at several places in the Rhone at Touron 
(Ardéche), and by MicHartsEeNn (6) in a warm-water tank of the Botanical Gardens at 
Hamburg. Perrier does not give any anatomical description of his specimens, while 
MIcHAELSEN states that, apart from the genital apparatus, which he describes in detail, 
his ppeonnene agree oe with Bepparp’s. 
the absence from them of the dorsal series of setie. The presence or absence of this cephalisation has hitherto, I think, 
always been regarded as of generic importance, and the extent anteriorly of the dorsal sete is always mentioned in th 
generic diagnoses of the Naidide ; and so BourNE, Bepparp (3), and MicHAgLSEN (5) all give the distribution of 
dorsal setze (as far forwards as the second segment) as a generic character of Chetobranchus. 
It is, 1 think, very possible, as 1 have myself suggested, that cephalisation will lose much of the importa 
hitherto assigned to it. But until the question has been further discussed, and until authorities are agreed 
respect to this far-reaching alteration in our ideas as to specific and generic characters in the Naidide, it seems be ter 
to abide by the more general opinion on this point. 
