xni PHOSPHORESCENCE GEOGRAPHICAL DISTRIBUTION 369 



to Giard, the light is produced by a series of glands in the 

 anterior region of the body debouching upon the exterior. This 

 same worm has since been found in other localities, where it has 

 been shown to be phosphorescent, by Moniez l and by Matzdorf. 2 

 It is remarkable that in some other cases the luminosity, though 

 it exists, is very rarely seen. The exceedingly common Brandling 

 (Allolobophorafoetida) of dunghills has been observed on occasions 

 to emit a phosphorescent light. This observation is due to 

 Professor Vejdovsky, 3 and was made " upon a warm July night of 

 1881." He thinks that the seat of the light is in the secretion 

 of the glandular cells of the epidermis, for when this and other 

 worms are handled the phosphorescence clings to the fingers, as 

 of course does the mucous secretion voided by the glands. 



Phosphorescence has been observed also in some other families 

 of Oligochaetes. The late Professor Allen Harker noticed a small 

 worm in marshy ground in Northumberland which emitted a 

 distinct light, and which was subsequently identified as a member 

 of the family Enchytraeidae. 



Geographical Distribution. 4 In the succeeding pages some 

 of the details of the geographical range of the Oligochaeta will be 

 found. The present section deals with a few generalities, which 

 appear to result from an examination of the facts. 



As to the aquatic genera but little is known at present with 

 regard to their range ; they have not been widely collected in 

 extra-European countries. What little is known points to the 

 conclusion that while many parts of the world have their peculiar 

 genera (such as Hesperodrilus in South America, Phreodrilus 

 and Pelodrilus in New Zealand), some of the common European 

 species are widely distributed. I have, for example, received 

 Henlea ventriculosa from Kirghiz Tartary, and from New Zealand ; 

 and a New Zealand Tubifex appeared to me to be indistinguish- 

 able from the common T. rivulorum of our rivers and ponds. It 

 is possible that these and similar instances may, at least in some 

 cases, be due to accidental importation at the hands of man, a 

 matter into which we shall enter later. But the aquatic genera 

 have, many of them, facilities for extending their range in a natural 

 fashion, which are greater than those possessed by earthworms. 



1 Rev. Biol. Nord France, i. 1889, p. 197. 2 SB. Ges. naturf. Berlin, 1893, p. 19. 



3 System u. Morph. d. Oligochaeten, Prag, 1884. 



4 See my text-book of Zoogeography (Cambridge, 1895) for fuller treatment. 



VOL. II '2 B 



