Harriet Randolph
The Pioneering Planarian Regeneration Experiments of Harriet Randolph

In 1897 while at Bryn Mawr College, Harriet Randolph published a paper entitled" Observations and Experiments on Regeneration in Planarians" (Arch.Entw. Mech. Org. 5: 352-372). The work was carried out during the summer of 1893 at the Marine Biological Laboratory in Woods Hole, Massachusetts. This paper is remarkable in several respects, two of which are that it provides a thorough and scholarly review of the history of planarian regeneration up to that time; and secondly, it goes on to describe a series of systematic amputations the author performed on these organisms. It is very likely that Randolph's work may have ignited T.H. Morgan's interest in planarians since at the time, he was an Associate Professor of Biology at Bryn Mawr College.

Below, several of the figures from Randolph's manuscript are presented to illustrate the variety of ways in which she cut planarians (Planaria maculata) to challenge their regeneration abilities.
Animals were cut transversely (Fig. 1) and longitudinally (Fig. 2) and in most cases, each of the obtained pieces was capable of regenerating the missing halves. Randolph also noted that head amputation also had the effect of being able to induce fission in the posterior halves (tails) of the animals since " there were six individuals more in the dish than there would have been if all the tail-pieces had regenerated".
In Fig. 4, the animals were cut both transversely and longitudinally. Randolph repeated this experiment several times and reported that " in all cases each piece lived. Regeneration of all the missing parts took place..."

In Fig. 5, the animals were cut transversely into eight different fragments and " all the missing parts were regenerated. The new individuals lived and seemed entirely normal..."
The experiment shown in Fig. 6 was designed to test the size limitations of planarian regeneration. As Randolph reported " a piece only large enough to be seen with the naked eye will develop into a perfect whole".

Later T. H. Morgan would show that a fragment 1/279th the size of the original organism is competent to regenerate a whole animal, thus confirming and extending Randolph's results.