20 EARTHWORMS AND LEECHES [CH. I 



as must frequently be inflicted by birds and others of its 

 natural foes. 



Friedlander 1 has shown that not only may a number 

 of anterior or posterior segments be regenerated, but also 

 the supra-oesophageal ganglia, and other parts of the 

 nervous system. The regenerating tissue consists of 

 masses of amoeboid cells, into which new growths make 

 their way. The new parts are always of reduced dia- 

 meter and exhibit frequent abnormalities. According to 

 Hescheler 2 in L. terrestris, L. rubellus, H. (A.) longus, 

 E.fcetida, H. (A.) caliginosus complete regeneration of the 

 anterior end is only accomplished when comparatively few 

 segments are lost : if the number exceed ten, some four or 

 five segments only are formed anew. Monstrous individuals 

 of L. terrestris and of E. foetida have been described by 

 Bell 3 , Marsh 4 , Williamson 5 and others. The monstrosity 

 in all cases consists in a doubling of the hinder region 

 so that the tail appears forked. The abnormality affects 

 all the chief internal organs. The branching usually takes 

 place at about three-quarters of the length from the head. 

 Each branch ends in a functional anus. 



Enemies and Parasites. Birds are proverbially the 

 worst enemies of earthworms, and chief among them may 

 be mentioned the thrush and rook, which are both equal 

 to devouring a full-grown worm, while robins, hedge- 



1 Zeit. wiss. Zool LX. 1895. 



2 Vierteljahrschr. Nat. Gesellsch. Zurich. XLII. 1897. 



3 Ann. Mag. Nat. Hist. (5) xvi. 



4 Amer. Nat. xxiv. 



6 Ann. Mag. Nat. Hist. (6) xm.; cf. also Broom, Trans. N. H. Soc. 

 Glasgow, u. N. S. 



