REVERSIBILITY OF MORPHOGENESIS 5 



From what precedes the following facts should be noted: (1) 

 Dedifferentiation followed by differentiation is a normal process 

 and at least from a morphological standpoint may be considered 

 reversible. (2) It is a distinct morphogenetic response which 

 occurs under a number of different conditions and to different 

 extent. 



III. INITIATION OF DEDIFFERENTIATION AND DIFFERENTIATION 

 1 . By cutting into two or more parts 



A large number of experiments were made in each of which 

 records of cut pieces from sets of twenty-five to one hundred in- 

 dividuals were taken at intervals varying from an hour to twelve 

 hours. In most cases the record of the condition of each piece 

 were continued until death, encystment or starvation of the 

 regenerated pieces ended the experiment. The individual to be 

 cut was placed in a small drop of water on a slide and cut, under 

 the low or high power of the binocular, with a fine pointed curved 

 scalpel. Anterior and posterior halves or right and left halves 

 are quite readily obtained in this way with a little practice. 

 The pieces were placed in separate watch crystals or depression 

 slides containing tap water and kept in moist chambers. Un- 

 fortunately a large number of the experiments designed to yield 

 quantitative data on such questions as the effect of size of 

 nuclear piece on regeneration, rate and capacity for regeneration 

 of pieces cut at different ages, etc., proved to be useless, except 

 in so far as they showed that the results depended largely on 

 the state of nutrition and previous history of the cell. It has 

 been impossible as yet to thoroughly control these in Bursaria 

 and hence the results did not show any definite uniformity. 



The results as far as they concern the normal process of regu- 

 lation of anterior and posterior pieces are summarized plate I, 

 figures 10 to 15 inclusive. Figure 10 is partly schematized for 

 the sake of clearness by showing the cut surface as it would 

 appear if it did not close. The other figures are close represen- 

 tations of the actual appearance of regenerating pieces at various 

 stages of dedifferentiation and differentiation. 



