THE ZOOLOGIST 



No. 861.— March 15th. 1913. 



A KEY TO BRITISH HENLEAS. 

 By the Rev. Hilderic Friend, F.L.S., F.R.M.S. 



When my brief paper on British Henleas appeared in the 

 Zoologist' (1911, p. 464), it was impossible to foresee that in 

 another year the number would be raised from eight to a score 

 and a half, and that a key would be necessary in order to enable 

 the student readily to distinguish one species from another. 

 Aided by a Government grant, however, it has been possible for 

 me to make many new discoveries in different parts of the 

 country, and in this way greatly to extend our knowledge of this 

 group of Enchytraeids. Having during the past year given a 

 somewhat full account of this genus in the ' Journal of the Royal 

 Microscopical Society,' and in other journals enumerated in the 

 Bibliography, it is not necessary to go over the same ground in 

 detail. Since, however, several new species have been found 

 since the principal of these articles was written, and some of 

 these species have not yet been described, the key would be of 

 little value without a few preliminary remarks. 



The genus Henlea pertains to the Enchytraeids, a family of 

 Annelids belonging to the order Oligochseta. One of its chief 

 characters is the forward position in which the dorsal vessel 

 arises, usually from or near a bulbous swelling of the intestine, 

 and the frequent presence of oesophageal glands in that locality. 

 It now appears that the dorsal vessel often arises in or near the 

 girdle, and it may be desirable eventually to separate the two 

 groups into different genera. At present, however, it suffices to 

 use this difference for purposes of classification within the genus. 

 Zool. 4th ser. vol. XVII., March, 1913. H 



