Galloway. — Dero vaga. 



PLATE 1. 



Fig. 1. Optical sagittal section of posterior portion of a worm not in process of 

 budding, showing undifferentiated preanal zone (z.). X 30. 



Fig. 2. Similar view of portion of an individual in which the bud zone (z. 1 ) is 

 already distinguishable. X 30. 



Fig. 3. Budding worm in which the secondary bud zone (z.-) is recognizable. 

 The Roman numerals indicate the number of the segment behind the 

 prostomium of the original worm; the Arabic, those of the zooids. 

 The accented Arabic numerals, T-4', denote the zone of undifferen- 

 tiated materials out of which are to be formed the cephalic segments 

 of the individual produced by the second budding. X 100. 



Fig. 4. Parasagittal section of a budding segment showing ectodermal thickening 

 and ingrowth on ventral surface only, at a fairly advanced stage. Sec- 

 tion considerably to one side of the median plane. X 655. 



Fig. 5. Parasagittal section of the whole segment at a later stage. X 218. 



Fig. 6. Cross section of a stage much more advanced than the preceding, through 

 the posterior zooid, showing the position of the brain (gn. su'oe.). X 218. 



Fig. 7. Transverse section of a similar stage, posterior to position of the brain, 

 showing the regions where the ectoderm grows in between the muscle 

 bands. X 218. 



