82 THE ZOOLOGIST. 



Thus we have for our guidance the presence or absence of salivary 

 glands, oesophageal glands, spermiducal glands, atrial glands, 

 and the like ; the shape of the brain, the point of origin of the 

 dorsal vessel, the structure of the nephridia, the ccelomic 

 corpuscles, the setae, and other characteristics. After careful 

 study of many hundreds of specimens from various parts 

 of the country, it has gradually been borne in upon me that, 

 while the setse in the genus Fridericia are so constant that they 

 can be absolutely depended upon as a species-character, the 

 setse in the Henleas are still in a fluctuating condition. In one 

 and the same species they vary widely in number, and this 

 applies to specimens collected at the same time in the same 

 locality, as well as to those taken at intervals from different 

 sites. Age and development have to be taken into account, and 

 it is of the utmost importance that final diagnoses be based 

 upon adults whenever possible. 



In my former article (1) * eight species of Henlea were 

 recorded as British, while a ninth was tentatively admitted in 

 an Addendum. My next catalogue (2) contained no fewer than 

 nineteen species, with the statement that " since this paper was 

 written in May, 1912, one new species has been found by me in 

 Ireland, making the twentieth British species." The description 

 of the twentieth species duly appeared in the ' Irish Naturalist ' 

 (3) for January, 1913, the creature being named Henlea glan- 

 dulosa, Friend. In the meantime further collections had been 

 made in Derbyshire, Nottinghamshire, and elsewhere, with the 

 result that other species apparently new to science were brought 

 to light. Some of these, which were first found in Nottingham- 

 shire, have been reported on in the ' Transactions of the Notts 

 Nat. Hist. Soc' (4). One has been named H. mariona on account 

 of its resemblance to certain species of Marionina, which was 

 formerly written Mariona. Others are very small, as the names 

 pusilla, parva, minuta, and the like are intended to imply. In 

 two or three species we find four pairs of septal glands, and in 

 one case there are three setae in each bundle throughout, for 

 which reason it is named H. trisetosa. 



In order that the key may be as complete as possible, it is 

 necessary to add a brief description of those species which have 



:: ' The numbers in brackets refer to the Bibliography. 



