54 HAROLD SELLERS COLTON. 



EXPLANATION OF PLATE II. 



Fie. 14. Section 6/t thick of the termination of a rectal tubule of Bolryllus 

 which was fixed in Flemming's solution. This shows a thin place in the wall of 

 the tube and also a vacuole. In this figure is also shown the relation of the tube 

 to the walls of the intestine. The vacuoles in the intestinal cells are those which 

 stained red and blue in ammonium carminate and in indigo carmin respectively. 

 X 1,000. 



FIG. 15. Drawing made from two adjoining sections of a rectal tubule, which 

 show terminations with both a thin place and a depression. X 1,000. 



FIG. 16. A section of a bud of Botryllus showing the origin of the pyloric gland 

 as an out pocket to the stomach. X 320. 



FIG. 17. Sections of the rectum of Bolryllus fixed in absolute alcohol, glacial 

 acetic acid and chloroform. This shows the relation of the tubes to the canal. 

 X 150. 



FIG. 1 8. Two living blood cells, in one of which the nucleus is visible in the 

 other it is not. X i.ooo. 



FIG. 19. Optical section of ampulla of Ascidia. X 1,000. 



FIG. 20. Optical section of rectal tubule of Ascidia. X 1,000. 



FIG. 21. Optical section of ampulla of Perophora. 'X 1,000. 



FIG. 22. Optical section of ampulla of Perophora. X 1,000. 



FIG. 23. Optical section of ampulla of Molgula. X 1,000. 



FIG. 24. Optical section of ampulla of Styela. X 1,000. 



FIG. 25. Optical section of ampulla of Styela, containing a concretion of indigo 

 carmin. X 1,000. 



FIG. 26. Optical section of a tube of the refringent organ of Styela containing 

 a concretion of indigo carmin. X 1,000. 



