32 DR J. STEPHENSON ON 
though not new, they have hitherto been recorded but once or a few times, and there 
are still lacune to be filled before our knowledge can be considered complete ; or lastly, 
as Enchytreus albidus, a well-known and widely distributed form, but at the same 
time one which appears to be very variable, and the Clyde specimens of which 
show peculiarities of their own. 
One further point may perhaps be noted here, rather than in the body of the paper 
namely, the relationship between the genera Lumbricillus and Enchytreus. 
The characters serving to distinguish these genera may be said to be four. (i.) The 
setee of Lwmbricillus have a double, or [-shaped curve ; those of Hnchytreus are straight, 
with, however, a small hook-like curve at their proximal end. (ii1.) The presence or 
absence of a penial bulb; Eisen (4) not only makes this a distinguishing feature between 
the genera, but proposes it as a chief means of dividing the Enchytreeidee into two sub- 
families, the Lumbricilline which have, and the Enchytreeine which have not this 
structure (cf. below, under Hnchytreus nodosus and Lumbricillus viridis). (iii.) The 
‘copulatory glands’ or ‘ Bauchmarkdriisen,’ are supposed to be distinctive of the genus 
Lumbricillus ; thus Bepparp (1) writes: ‘One of the most characteristic structural 
features of the genus, though confined to a few species, is the outgrowths of the ventral 
nerve-chord in certain segments.” (iv.) The multilobed testes of Lumbricillus are also 
one of its chief generic characters. 
If certain of the forms here described be examined with regard to these characters, 
the following conditions are found: Lumbricallus viridis, while in the other points 
showing a typical Lumbricilline structure, has, in the anterior part of its body, sete of 
the typical Hnchytreus form, while the posterior setze show only a very faint double 
curvature. Hnchytreus nodosus, though its sete are for the most part typically those 
of the genus in which | have placed it, shows in certain cases setee with an indication 
of a double curvature, copulatory glands, and a penial bulb, 7.e. Lumbricilline characters 
are present; the testes, however, are single on each side. Hnchytreus dubius has setee 
which are throughout similar to those described as typical for the genus to which I have 
referred it; while in the possession of lobed testes, copulatory glands, and a penial bulb 
(though this latter is bifid internally), it agrees with Lumbricillus ; I may add that it 
has red blood, a feature commoner in the species of Luwmbricillus than in those of 
Enchytreus. Finally, Enchytreus albidus, a very fairly typical species of its genus, 
has nevertheless an imperfect penial bulb, surrounded, it is true, by other and smaller 
ageregations of gland cells (cf below, under LE. nodosus). 
It would therefore appear that not only are the two genera closely allied, but that a 
number of intermediate forms exist which serve to bridge over the interval between 
the two.* 
* With regard to the existence of copulatory glands in the genus Hnchytreus, SourHERN has recorded their 
occurrence in £, lobatus ; and there is also a penial bulb in this species (14). 
