Preliminary Laboratory Experiments on Recruitment and Mortality in Triclad Populations

Summary

1.	Recently-hatched young of Dugesia lugubris (O. Schmidt) and Polycelis tenuis (IJIMA) Were able to survive better than shrunken adults of comparable size when kept together under conditions of food shortage.
2.	Under similar conditions large specimens of both species were Superior to recently-hatched young.
3.	In both species ability to survive without food was related to initial size and adults were able to survive for 33–41 weeks. Minimal survival size was also related to initial size, large specimens were not able to shrink to such a small size as smaller specimens.
4.	Adults of D. lugubris were able to survive the stresses of starvation, rapid changes in temperature and ionic content of water and reproduction without mortality.
5.	The implications of these results for natural populations are discussed.