26 
Proceedings of the Royal Society of Edinburgh. [Sess. 
chaetae are slightly larger than the transverse diameter of the body : 
unfortunately those figured are from a stained preparation, in which the 
arrangement is slightly distorted. As regards the internal anatomy, the 
only specimen of which I possess sections was in a sexual condition, 
although the ova were not ripe. 
The testes are in segment V ; the vas deferens opens into a glandular 
atrium in segment VI. Paired receptacula seminis were present in V. 
I am not quite clear as to the arrangement of the vesicular seminules, 
but a dorsal median sac was present in segment IV. 
Paired ovaries were found on septum 5/6. The structure of the gut and 
nephridia appeared to correspond with that found in Stylaria proboscidea. 
The circulatory system was well developed, and the dorsal vessel was 
present in the posterior segments (fig. 2), a character which, according to 
Vejdovsky, differentiates Stylaria from the other Naids. 
Most recent systematists place Stylaria lacustris (Linn.) in a distinct 
genus (Vejdovsky, Bourne), but Beddard considers it congeneric with 
Nais elinguis. It appears to me that it would be best, with Vejdovsky, to 
make one genus, Stylaria, including Stylaria lacustris, Lomondi and the 
somewhat doubtful genus Ripistes or Pterostylarides. 
The only character which separates Pterostylarides from Stylaria, 
according to Bourne, is “ the peculiar character of the cephalization,” by 
which he means the possible absence of ventral chaetae in segments IV, V. 
Bourne himself admits that “the idea that the region between the 
second and third seta-bearing segments does represent two segments is an 
assumption 55 ; and even if it existed, I cannot see how the term cephalization 
is applicable to the absence of seta on two intermediate segments of the 
anterior region of a worm. 
Diagnosis — Stylaria Lomondi. 
Rather stout forms about 10 mm. long, with a short proboscis and eyes. 
Fine capilliform setae (12-16), arranged in a fan-shaped manner in the 
dorsal bundles, beginning in segment V. Ventral bundles throughout the 
animal’s length, 6-8 sigmoid forked chaetae. 
