Pressure upon the Regeneration of Gunda ulvse. 1 9 



5. Under starvation conditions, G-. ulvce undergoes reduction. This consists 

 in (1) absorption of the genital system, (2) general reduction in size. Both 

 these are brought about by the activity of the parenchyma cells. 



6. During the process of restoration of lost parts the same reduction 

 processes occur as in starvation. Where the restoration of lost parts is 

 retarded, e.g., by raising or lowering the osmotic pressure, reduction is 

 retarded to precisely the same extent. 



7. In sea-water or hypertonic solutions removal of the posterior half of 

 the body inhibits further production of sperm. In hypotonic solutions sperm 

 continues to be produced for a varying length of time. 



8. In strongly hypertonic solution examination of the gut cells shows that 

 these have diminished in size and become more dense. In strongly hypotonic 

 solutions they have increased in size and become vacuolar. 



I should like to take this opportunity of thanking the director and staff 

 of the Plymouth laboratory for the promptness with which they have 

 supplied me with material, and for their unfailing kindness during the 

 whole time I have worked at the laboratory. I should like also to 

 acknowledge my indebtedness to the Koyal Society, the Zoological Society, 

 and the University of Cambridge for the use of their tables at Plymouth. 

 Finally, I wish to thank the Trustees of the Balfour Fund for a grant 

 which made it possible for me to take up the work in 1912. 



BIBLIOGEAPHY. 



1. Bardeen, C. B., "Embryonic and Begenerative Development in Planarians," 'Biol. 



Bull.,' vol. 3, p. 262. 



2. Child, C. M., " Experimental Control of Morphogenesis in the Begulation of 



Planaria," 'Biol. Bull.,' vol. 20 (1911). 



3. Curtis, Winterton C, " The Life History, the Normal Fission, and the Reproduc- 



tive Organs of Planaria maculata," 'Bost. Soc. Nat. Hist. Proc.,' vol. 30, p. 515 

 (1902). 



4. Flexner. Simon, " Regeneration of the Nervous System of Planaria torva" ' Journ. 



Morphol.,' vol. 14, p. 337 (1898). 



5. Iijima, I., " TJntersucliungen iiber den Bau und die Entwicklungsgeschichte der 



Siisswasser Dendrocoelen (Tricladen)," ' Zeitschr. f. Wiss. Zool.,' vol. 40, p. 359 

 (1884). 



6. Jordan Lloyd, D., " The Influence of the Position of the Cut upon the Regeneration 



of Gunda ulvce," ' Roy. Soc. Proc.,' B, vol. 87, p. 355 (1914). 



7. Knudsen, Martin, ' Hydrographical Tables,' London and Copenhagen, 1901. 



8. Kriimmel, Otto, ' Handbuch der Ozeanographie,' vol. 1, p. 240, Stuttgart, 1907. 



9. Moi'gan, T. H, "Growth and Regeneration in P. lugubris? 'Arch. Ent. Mech.,' 



vol. 13, p. 179 (1901). 



10. Przibram, H, "Equilibrium of Animal Form," 'Journ. Exp. Zool.,' vol. 5, p. 259 

 (1907). 



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