388 OLIGOCHAETA 



Miiller. This worm, which is universal, or nearly so, in its 

 range, doubtless having been transferred accidentally from country 

 to country, invariably shows a light spot noi far from the tail ; 

 when this is examined with the microscope it is seen that the 

 chaetae are here absent or very small, and that the muscular 

 structure of the body-wall is slightly different ; it was thought 

 that this spot was a zone of growth where fresh segments could 

 be added after the fashion of some of the aquatic Oligochaeta, to 

 which, it may be remarked, the present genus shows a curious 

 point of likeness in the bifid character of the chaetae. It seems, 

 however, that there are really no grounds for the supposition, and 

 it is possible that we have here a " weak " spot, such as that in 

 the foot of certain land snails, which readily gives way when the 

 worm is picked up by a bird, and allows the " better half " of the 

 creature to escape. The Bermudian genus Onychocliacta offers a 

 very strange peculiarity in that the chaetae on the hinder seg- 

 ments of the body are enormously larger than those in front, and 

 end in strong hooks ; it seems likely that their function is to 

 maintain a tight hold of the ground while the worm is leaning 

 out of its burrow, as every one has seen the common earthworms 

 of this country do. Onychocliaeta has the same irregular arrange- 

 ment of the chaetae upon the greater part of the body, as has 

 Pontoscolex. This family, like so many others, has its giants and 

 its dwarfs. At one extreme is the great Antaeus of South 

 America, several feet in length ; at the other the inch-long Hyo- 

 genia of Africa. The American Urobenus has a pair of intestinal 

 caeca like those of Perichaeta, and placed in the same segment. 



FAM. 14. Lumbricidae. 1 This family is to be distinguished 

 by the following assemblage of characters. 



The male pores are usually upon segment 15, and never 

 behind that segment; the clitellum commences some way behind 

 the male pores. The gizzard, which is invariably single, is equally 

 invariably at the end of the oesophagus. There are three pairs 

 of calciferous glands. The nephridia are always paired. The 

 spermathecae never have a diverticulum. 



This family only contains three well-known genera, viz. 



1 Rosa, "Rcvisione dei Lumbricidae, " Mem. Ace. Torino (2), xliii. 1893, p. 399 ; 

 also the Rev. H. Friend's numerous and useful papers, and especially "A New 

 Species of Earthworms," Proc. Jloy. Irish Ac. (3) ii.' 1891-93, p. 402 ; and "The 

 Earthworms of Ireland," Irish Nat. v. 1896, p. 69, etc. 



