3422 



THE WORM-LIKE ANIMALS 



external layer of cells becomes transformed into the cuticle, and the mouth appears 

 as a depression at the end of the blunt head. When the muscular system and ali- 

 mentary canal are developed, the embryo hatches in the form shown in the bottom 

 right-hand figure. Most of the species lead a parasitic life, chiefly in animals; 

 many, however, are free-living forms, occurring in damp earth, fresh water, and the 

 sea. A genus, with marine habits, has received the name of Enoplus, and includes 

 small, slim, transparent creatures, some of which are provided at the front end with 



DEVELOPMENT OE THREADWORM, Nematoxys. 

 (Enlarged 400 times. ) 



isolated bristles (as illustrated on p. 3421), while many are furnished with 

 a peculiar spinning gland, opening beneath the tail. According to Schneider, "as 

 soon as the animal has fixed its tail to something it moves on, and draws after it 

 the secretion in a transparent thread, which is often several lines long. One end 

 of this thread sticks fast, and by the other the animal floats freely in the water." 

 The young are found in shallow water, and may be seen crawling on the surface of 

 seaweeds; but the mature animals occur at depths of from two to three fathoms. As 



