H. Friend 199 



is shared by other genera, and that the line of demarcation is anything 

 but sharp and clear. But it must at the same time be noted that if 

 we limit the genus as suggested the oesophageal glands, coelomic 

 corpuscles, and brain are distinct characters separating Henlea from 

 every other genus. Buchholzia and Bryodrilus will then be the only 

 genera at all likely to prove confusing and these can be distinguished 

 by characters which are perfectly definite and satisfactory. 



If now we look at one of our indigenous species which approaches 

 most nearly the typical form, and subject it to a very careful and 

 systematic examination, we shall have a standard by which all the 

 other species may be tested. A suitable type presents itself in the 

 case of Henlea fragilis Friend, and we chose it partly on account of 

 certain points of interest attaching to its life-history and distribution. 



Henlea fragilis was first found by the author at Bopeep, St Leonards- 

 on-Sea, on December 21st, 1911, against the walls of an arch through 

 which a streamlet flows into the sea. Along with it were several other 

 new species, which were described (3) in the Journal Roy. Micros. Soc. 

 for 1912 (pp. 586-598). The claims of this species to special recognition 

 lie, not alone in its typical character, or in the fact that I have been 

 able to obtain abundance of living material for microscopic investigation, 

 but also in the following curious coincidence. 



In the summer of 1914 a box containing living specimens of Peripatus 

 for research was received at the Birmingham University. As it was 

 found on examination to contain a large number of Enchytraeids, 

 Professor Gamble, F.R.S., kindly handed the material over to me for 

 investigation. The white worms proved to belong to various species 

 and genera, and among them were several finely developed and fully 

 mature specimens of Henlea fragilis. The question, how the worms, 

 which had been found by me previously in Sussex, came to be included 

 in earth from Cape Town is one which may be discussed elsewhere. It 

 suffices to say that I was in possession of excellent material both for 

 the study of the living worm and for the preparation of sections, and 

 could therefore produce a fuller and more detailed account of Henlea 

 than had hitherto appeared. 



In February, 1915, Mr Cox, Steward in the Department of Zoology 

 at the Birmingham University, prepared for me an excellent series of 

 sections both transverse and longitudinal-vertical, and it is upon the 

 study of these sections, carefully checked by a constant reference to the 

 living worm, that the following details are based. The illustrations 

 which accompany the paper have all been made from the microscopical 



