2^yS W. S. NICKERSON. 



EXPLANATION OF PLATE XXXIL 



Fig. I. Ventral view of large adult represented as an opaque object ; the 

 lophophore is partially retracted, x 59. 



Fig. 2. Transverse section of a strongly contracted male specimen, x 114. 



Fig. 3. A portion of the margin of the lophophore, outer surface, showing bases 

 of five tentacles, two of which are extended and the other three folded inward 

 beneath the margin of the lophophore. X 160. 



Fig. 4. Portion of a total preparation, dorsal aspect, showing relations of the 

 brain, the ovaries and their ducts, the shell gland, the excretory organs, and the 

 digestive tract. X 205. 



Fig. 5. Sagittal section through upper portion of body showing mammary 

 organ in condition of highest development. X 205. 



Fig. 6. Portion of transverse section through intestine and sexual organs ; in 

 the gonad on the left side of the figure is shown a degenerating ovum surrounded 

 by a mass of cells showing various stages in the formation of spermatozoa. 

 X 255. 



Fig. 7. Sagittal section of a fully expanded individual, x 165. A portion of 

 an embryo attached to the mammary organ is shown in this section. 



Fig. 8. A few cells of the dorsal band showing appearance when more highly 

 magnified, x 675. 



Fig. 9. Transverse section of a tentacle, x 675. 



Fig. 10. Transverse section through base of a tentacle showing unicellular 

 sucker, x 675. 



Fig. it. View of individual with fully expanded lophophore and four buds, 

 the parent and the two larger buds having flask organs. X 57. 



Fig. 12. The digestive tract from a total preparation, dorsal aspect. X 57. 



Fig. 1 3. Section of ovary containing a nearly mature ovum, x 480. 



Fig. 14. An abnormal bud drawn as an opaque object, x 250. 



Fig. 1 5. Portion of stalk and foot as seen from ventral side ; showing glands 

 in foot and oblique muscle fibers on anterior side of stalk. 



