78 INTRODUCTION TO ZOOLOGY chap. 



little pores in segment 14, and also a number of sperm cells 

 which have been obtained previously from another individual, 

 but temporarily stored in this worm in certain little recep- 

 tacles in segments 9 and 10. With the ova and sperms is 

 deposited some albuminous food-stuff on which the young 

 worms will feed during their early development. 



As soon as the body of the worm is withdrawn the two 

 ends of the "cocoon" close, shutting in the contents. The 

 cocoons are at first white, but soon turn yellow or brown. 

 One end is rounded and the other usually somewhat drawn 

 out (Fig. 37, (7). Although there may be several eggs in the 

 cocoon, only one, as a rule, completes its development, grow- 

 ing at the expense of the others. The little worm is perfect, 

 though minute, when it makes its way out of the cocoon. 

 Tjjg Most dangerous of the enemies of worms are 



Enemies those birds, such as the thrush and blackbird, as 



of Worms, ^gjj ^g many smaller birds, which pull the worms 

 out of their burrows, and devour an enormous number of 

 them. When venturing above ground, they constantly fall 

 a prey also to hedgehogs, toads, frogs, lizards, and many other 

 creatures who, living mainly on insects, have recourse at times 

 to worms to supplement their otherwise somewhat unsub- 

 stantial diet. Some beetles, such as the " Devil's Coach-horse " 

 (see p. 252), feed largely on them. Some centipedes, and 

 the little carnivorous shell-bearing slug Testacella, follow and 

 attack them underground, as does also the mole — the tiger of 

 the underworld — a creature needing apparently a vast amount 

 of food to enable it to live its extremely active life, and finding 

 a large proportion of this food in the worms which inhabit 

 the same strata of soil as itself. 



Regenera- In speaking of the dangers to which Earth- 

 tion. worms are exposed, it is interesting to note the 

 very great power of regeneration of tissues arid recovery 

 from wounds that they possess. The loss of any number of 

 segments from the back end of the body can be made good, 

 the lost segments being regenerated from a special tissue 

 which arises at the cut surface. The new part can usually be 

 easily detected by its paler colour and reduced diameter. 



According to Kescheler,^ the complete regeneration of the 

 front segments on the hinder severed portion is more doubtful, 



1 Kescheler, Viertdjahrschr. Nat. Gesdlsch., xlii., Zurich, 1897. 



