290 



IV. Discussion of Results. 



1. The whole stem and the hydranth may be reproduced after a 

 cut through the stalk at any of the levels. 



2. A few rings only and the hydranth may be produced after a 

 cut through the stalk at any of the levels. 



3. The nearer the cut to the proximal end of the stalk, the 

 greater the percentage of cases of reproduction of an entire stalk (with 

 unsegmented tract). The figures are: After a cut at level y an un- 

 segmented tract is produced in 3% of the cases; at level ß in41°/ ; 

 at level a in 47 %• 



4. The nearer the cut to the distal end of the stalk (a), the 

 greater the de fin it en ess of regeneration (b), the less the mean 

 number of riDgs regenerated, and (c) the smaller both the upper and 

 lower limit in the number of rings regenerated. 



a) There is no single well-marked maximum in the regeneration 

 following the a cut ; but, on the contrary, three maxima appear, namely, 

 at 6 rings, 10 rings and 14 rings. After a ß cut, there is a principal 

 maximum at 6 rings and a secondary one at 9 rings. After a y cut, 

 there is an extremely expressed maximum at 4 rings, the secondary 

 maximum at 9 rings being relatively inconsiderable. 



b) The mean number of rings is obtained by multiplying each 

 number regenerated rings by the number of cases in which it occurs, 

 and dividing the sum by the total number of cases. This gives the 

 mean number of rings regenerated after a cut at level a equal 9,4; 

 at level ß 7,5; at level y 4,3. 



c) After an a cut, regeneration occurred between the limits 4 — 18; 

 after a ß cut 2 — 18; after y cut 2 — 14; both limits having decreased 

 slightly after the y cut as compared with the a cut. 



These facts stand out still more prominently by the use of 

 Galton's 1 ) graphical method of expressing distribution. The numbers 

 given in the fourth column of the tables — "Percentages: Sums from 

 the beginning" — obtained by adding the percentages of the third 

 column as far as the horizontal line on which the number in the 

 fourth column lies, are expressed graphically by rectangular coordinates: 

 the abscissas representing per cents and the ordinates the number of 

 rings regenerated. 



1) Feancis Galton, Natural Inheritance, London, Macmillan & Co., 

 1889, p. 37. 



