1907. Southern. — Oligochceta of Lambay. 77 



the nephridium rises near the front end, or middle of the post-septal. 

 Vejdovsky (1., PI. vii., fig. 4) figures it as rising near the posterior end 

 The dorsal vessel rises in the 21st segment. In one specimen there were 

 three diverticula on one spermatheca. four on the other. 

 Distribution. — Ireland. Europe. 



Achseta minima, n. sp. 



Only one specimen of this new worm was found in soil from Lamba}-. 

 Fortunately it was fully mature when I found it in June. Owing, how- 

 ever, to its small size and fragile nature, only a brief examination of the 

 living animal was possible. After it was stained and mounted, some of the 

 organs could not be made out clearly, and the description of them must 

 be left over till more material is available. Sufficient was seen to mark 

 it as a distinct species of this remarkable genus. 



Achcvla minima is a minute, transparent worm, 3 mm. long. Number of 

 segments 22. A large head-pore is present at the tip of the prostomium. 

 Of the internal glands representing the setse only the dorsal pair are 

 present. These are oval cells with the nucleus at the distal end (PI. 18, 

 fig- 3 B). The epithelium is faintly dotted with glands. The girdle 

 occupies the 12th segment. Its glands are in transverse rows. The brain 

 is about ii-2 times as long as broad. It is convex before and behind 

 The sides converge to the anterior end, which, in the preserved state, is 

 much narrower than the posterior. The ganglia of the ventral nerve 

 cord are very conspicuous when stained. The ganglia of the first four 

 segments are united into a single large mass (fig. 3 E, a). The edges of 

 the ganglia appear to be curved round to the ventral side (b). The septal 

 glands lie in the 4th, 5th, and 6th segments, those in the 6th being very 

 large. The coelomic corpuscles (fig. 3 A) are circular discs, nucleated, 

 coarsely granular, and brown in colour. The salivary glands could not 

 be made out with certainty. The alimentary canal is covered with large 

 brown cells. The dorsal vessel rises in the 6th segment, and there are 

 three dilations in the 6th, 5th, and 4th segments, those in the 6th and 

 5th being very large. The nephridia (Fig. 3 D) commence in the 6/7 

 septum. The auteseptal is almost semicircular in outline, with a straight 

 anterior border. The post-septal is 4-5 times as long, and is not distinct 

 from the duct. The duct is not dilated, and there are no glands at the 

 external pore. The sperm-funnel is 4-6 times as long as broad. The 

 duct is long and spirally wound, as in A. Eiseui, but more loosel}'. The 

 spermathecae (fig. 3 C) are simple sacs lying in the 5th segment, and 

 opening veutrally. They lie at the sides of the oesophagus. There is no 

 distinction between ampulla and duct. 



This species is most nearly related to A. bohemica (Vejrk), which it 

 resembles in only having the dorsal setal glands developed, and also in 

 the vascular system. It is distinguished from it by its small size, cOelomiC 

 corpuscles, nephridia, and spermathecae. 



