NEREIS AND ITS ALLIES 147 



is Euglycera. 1 Its proboscis has four jaws, situated at the 

 corners of a square, instead of two as in Nereis. The pointed 

 head and powerful writhing muscles enable the animal to 

 burrow with great rapidity (Fig. 132). 



A second kind, Autolytus, 2 is a small animal which 

 lives in little tubes attached to algse or hydroids (Fig. 

 133). The parapodia at the anterior 

 half of the animal are different from 

 those at the posterior half, for the 

 latter are large and fitted for swim- 

 ming. Eventually one of the middle 

 segments of the body becomes trans- 

 formed into a head, with eyes and 

 tentacles, then the whole of the hinder 

 half breaks off spontaneously. The 

 newly formed head is now the head 

 end of the new individual. This 

 individual leads a different kind of 

 life from the half which remains in 

 the tube, for it swims freely in the 

 water. The separated individuals are 

 either male or female, whereas the part 

 which lives in the tube never pro- FlG . 133. -Autolytus, 



duces eggS, but merely forms a new representative of a fam- 

 , ., '. ,, ,, , , -T . _ ily of Polychfeta in 



tail every time the old tail is cut oft wh i c h the animal buds 

 to form a sexual individual. off male or female in- 



;%.,,., dividuals from its hinder 



A third kind, Lepidonotus 3 is 'end. bud, head of the 

 characterized by the possession ot budded individual. After 



A. Agassiz. 



1 e&, typical ; FXike/ra, a woman's name, also applied to a family of 

 Polychseta. Euglycera means typical of the family Glyceridae. 



2 atfr6s, self ; Xtfw, to separate ; hence, self-separating. 



3 Xe7r/s, scale ; J/WTOS, back. 



