159.
[169] Dr.Cobbold has informed the Author that he has never observed a planaria divide spontaneously, and he is sceptical as to that process taking place at all.

Dr.H.Charlton Bastian has also stated that, in spite of much observation, he has never seen the process in _vorticella_.
[170] Professor Huxley's Hunterian Lecture, March 16, 1868.
[171] Ibid.

March 18.
[172] "Principles of Biology," vol.ii.p.

105.
[173] "Principles of Biology," vol.ii.p.

203.
[174] Quoted by H.Stannius in his "Handbuch der Anatomie der Wirbelthiere," Zweite Auflage, Erstes Buch, Sec.