360 G. E. GATES. 



crated at one end a new head containing thirteen segments and a 

 prostomium and at the other end a tail two and one-half milli- 

 meters long, containing in addition to the anal segment and the 

 growing region twelve differentiated segments. 



F. A shorter portion from the posterior half of another worm 

 regenerated at one end a head and at the other end a single anal 

 segment. 



G. A short tail fragment regenerated at its injured anterior 

 end a structure exactly similar in appearance to the tail developed 

 at the cut posterior surface of an anterior piece. 



H. The nine anterior segments containing both pairs of sper- 

 mathecae were removed from worm 82. Eight segments regen- 

 erated. Characteristic spermathecal pores appeared in interseg- 

 mental furrows 6/7 and 8/9 (the posterior pair of pores being 

 located between the last of the old and the first of the new seg- 

 ments ! ) . 



/. Several other worms from which anterior ends containing 

 one or both pairs of spermathecse had been removed regenerated 

 heads with one or two pairs of spermathecal pores at various in- 

 tersegmental levels. These worms were killed three weeks after 

 the operation, hardened in formalin and dissected. Definitive 

 spermathecae had not been formed by that time. The site of each 

 spermathecal pore was marked internally by the presence of a 

 lump of soft spongy tissue. Some of these specimens with re- 

 generated spermathecal pores were very similar to specimens of 

 this species secured by Beddard (1886) from the Philippines. It 

 is quite possible if not probable that many or even all of the thir- 

 teen anomalies described and figured by Beddard as " variations " 

 were the result of regenerative processes. 



/. Seventeen anterior segments were removed from worm 149. 

 When the animal was killed at the end of the fourth week after 

 the operation, seventeen segments had been regenerated. In the 

 usual position on segment fourteen was a typical female pore. 

 The clitellar segments (xiii-xvii) were distinctly lighter in color 

 than the other new segments, indicating the beginning of clitellar 

 differentiation. Although the head was carefully fixed and hard- 

 ened the tissues were too soft and spongy internally for dissection 

 and no reproductive organs could be demonstrated. 



