H. Friend '207 



origin. This reduces the number of genuine Henleas known to be 

 British (3) to 10 species, viz. attenuata, fragilis, fridericioides, heterotropa, 

 hibernica, nasuta (= leptodera), pusilla, quadrupla, triloba and ventriculosa. 

 These species vary in relation to the number, shape and arrangement 

 of their setae, the character of their coelomic corpuscles, the presence 

 or absence of glands to the spermathecae at the opening between 

 segments 4 and 5, the number and position of the taste organs or tongues, 

 the salivary glands, the shape and dimensions of the sperm funnels, 

 the nature of the penial bulb, and the point of origin of the dorsal 

 vessel. In H. ventriculosa two pairs of oesophageal glands are present, 

 the other nine species having one pair only. H. fridericioides possesses 

 glands to the spermathecae, which also sometimes occur in H. hibernica ; 

 but as a rule they are absent. Diverticula have never yet been found 

 on the spermathecae of British species. In H. quadrupla there are 

 four pairs of septal glands while as a rule three pairs only are present. 

 On the whole H. fragilis approaches Southern's H. hibernica more 

 nearly than any other British species. This may be shown as follows : 



H. fragilis Friend. H. hibernica Southern. 



Length 15 mm. 15-20 mm. 



Segments 55-60 55-60 



Setae 4-8 5-9 



Oesophageal glands One pair in seg. 8 One pair in seg. 8 



Dorsal vessel 8/9 8/9 



Contractile swelling* 6, 7. 8 6, 7, 8 



The brains are also of the Henlean type. But while hibernica is 

 opacpie, fragilis is transparent ; hibernica often has small spermathecal 

 glands which are not found in fragilis; the sperm funnels of hibernica 

 are three or four times as long as broad, and the pair of salivaries are 

 ventral, whereas in fragilis one is ventral and the other dorsal, while 

 the sperm funnels are only slightly longer than broad. If we look 

 particularly at the salivary glands we have to go to America for a case 

 similar to that of H. fragilis. While no other true British Henlea has 

 yet been found whose salivary glands are so arranged, Welch (8) has 

 recently described species (H. moderata and H. urbanensis) which show 

 the same feature. But in the former four taste organs are present, 

 there is only one oesophageal gland, and the dorsal vessel arises in the 

 9th segment, while in the latter there are two taste organs and the 

 dorsal vessel again takes its rise in segment 9. For the present therefore 

 we are content to allow H. fragilis to stand related to H. hibernica on 

 the one hand and //. moderata and H. urbanensis on the other. 



