304 °"'- 



the commissure. The worm from which this section was taken was fixed in corrosive 

 sublimate and stained in hsematoxylin. Spencer y^ hom. imm. obj. and Leitz oc. 3. 



Fig. 19. Cross-section of the brain commissure from a section of a worm treated 

 by Kolliker's method. Spencer Jg hom. imm. obj. and Leitz oc. 3. 



Fig. 20. The anterior end of a horizontal section of a worm which had been 

 treated by Kolliker's ('90) method. The section is not exactly horizontal, but is 

 inclined so that the left ciliated pit comes in the sections dorsal to the one figured. 



Fig. 21. Lateral nerve connecting the brain ganglia of two buds, — from a longi- 

 tudinal section of a worm which had been fixed in corrosive sublimate and stained in 

 borax carmine. 



Fig. 22. Cihated pit taken from a cross-section of a worm which was fixed in 

 chrom-osmic-acetic acid and stained in alum carmine. Spencer -^q hom. imm. obj. 

 and Leitz oc. 3. 



Fig. 23. Mass of parenchyme cells forming the beginning of the new pharynx of 

 a bud, — from a sagittal section of a worm which was fixed in corrosive sublimate and 

 stained in borax carmine. Spencer yV hom. imm. obj. and Leitz oc. 2. 



Fig. 24. A part of a sagittal longitudinal section of a worm showing the newly 

 formed pharynx of a bud before its lumen has opened to the outside. This section 

 is from a worm which was fixed in chrom-osmic-acetic acid and stained in hsematoxy- 

 lin. Spencer ^^ hom. imm. obj. and Leitz oc. i. 



Fig. 25. The dish-shaped organs from a section of a worm which was fixed in 

 chrom-osmic-acetic acid and stained in hematoxylin. Spencer y^ hom. imm. obj. 

 and Leitz oc. 3. 



All of the drawings were made with an Abbe camera. 



