86 TBE ZOOLOGIST. 



vessel arising at the base of the pair of cesophageal-glands, i. e. 

 in 8-9. 



The Addendum to my article in the ' Zoologist ' (1911, 

 p. 468) refers to this species under the title H. tenella. 



Found at Acresford, near Ashby-de-la-Zouch, November 28th, 

 1911, and the same week at Overseal, the adjoining parish. Also 

 Netherhall, November 22nd, 1912, and Bretby, February, 1913. 



6. Henlea trisetosa, sp. nov. 



A small worm, measuring about 5-6 mm., with 35-40 seg- 

 ments. Setae sigmoid, 3 in each set throughout. Like the last 

 it has 4 pairs of septal glands, but there are no oesophageal, so 

 that it falls into the Henleanella group. The dorsal vessel arises 

 in 9-10. The most advanced pair of nephridia found was in 

 8-9 ; small ante- and large post-septal, with duct as long as the 

 latter arising from the neighbourhood of the septum. Brain 

 about as long as broad, of normal type. No salivary glands. 

 Coelomic corpuscles not of the horny type. 



We may now proceed to notice some of the methods by which 

 the ever-increasing number of species may be distinguished. 



The Set^. — In the genus Fridericia one is able in many 

 instances to come to a definite conclusion, merely by the study 

 of the setae in front of the girdle. Where 4, 6, or 8 setae occur 

 in each bundle, the innermost are the shortest. It often 

 happens that this diversity occurs also among the Henleas ; but 

 the rule is not a constant one, and the setae of Fridericia differ 

 in shape from those of Henlea. Generally speaking, we may 

 say Henlea setae are needle-shaped, Fridericia setae are crochet- 

 hooked, Enchytrceus setae are sigmoid. The species which have 

 shorter inner setae are H. dicksoni, H. nasuta, H. ventricidosa, 

 H. variata, H. mariona, and H. fridericioides, with possibly 

 some others. 



The Brain. — As with the setae, so with the brain ; Fridericia 

 and Henlea each has its type. In Fridericia it is very rarely 

 concave behind, whereas in Henlea it is almost always so. 

 Wlien the brain of Henlea appears otherwise than concave behind 

 it is nearly always due to tension or position. It must always be 

 viewed from above, and is usually somewhat longer than broad. 



(Esophageal Glands may be present or absent. When pre- 



