380 W. S. NICKERSON. 



EXPLANATION OF PLATE XXXIII. 



Fig. 16. Longitudinal section of a mature flask organ, x 495. 



Figs. 17, iS. Sections showing two stages in the formation of flask organs. 



X 675- 



Fig. 19. A flask organ in which the gland cells have discharged their contents. 

 X 495- 



Figs. 20-22. Three consecutive transverse sections showing relative positions 

 of the gonads and their ducts, the median unpaired chamber (sent, ves^, the shell 

 gland, the brain, and the duct from the excretory organ. X 250. 



Fig. 23. Portion of sagittal section showing manner in which young embryos 

 are attached to parent, x 250. 



Fig. 24. An optical frontal section of stomach showing lateral glandular tracts 

 near basal end. X 114. 



Fig. 25. Rounded corpuscles from parenchyma, x 675. 



Fig. 26. Two mature spermatozoa from seminal vesicle. X 1280. 



Fig. 27. Portion of nearly sagittal section through upper portion of body to 

 show relations of oesophageal gland cell, x 250. 



Fig. 28. Oesophageal gland cell shown in Fig. 27, more highly magnified. 

 X 675. 



Figs. 29-31. Three consecutive sections through brain and adjacent organs of 

 bud still attached to parent ; showing a pair of bipolar cells connecting brain and 

 ventral wall of body. X 675. 



Fig. 32. Section through stalk of bud showing attachment to parent, x 495. 



Fig. 33. Section through excretory organ and duct. X 495. 



Fig. 34. Portion of margin of foot showing sucker-like openings of gland 

 cells. X 250. 



