CLASSIFICATION OF THE PRIMORDIA 75 



all these properties may be expressed by measurement. In the 

 present work the internal properties of the cells are passed over 

 in silence ; therefore I content myself with a simple mention. 

 (See §§ 60, 72, 73.) 



§58.— FIRST EXAMPLE: SPIROGYRA [continued).— 

 The mentioned primordia of an adult Spirogyra (or a similar 

 plant) may be classified with reference to their development in 

 the following way (see § 46) : — 



(i) The properties (i), (2) and (5) are original, arrested and 

 persistent. 



(2) The property (3) (differentiation) is arrested and persistent. 

 It may be looked upon as being an awakening property ; it does 

 not exist as long as the cells are only two in number (both being 

 terminal) and it is not produced by a transformation of a 

 previously existing property. 



(3) The property (4) (form) is arrested and persistent for all 

 the cells. It may be looked upon as being awakening. (I don't 

 take into account certain peculiarities of Spirogyra.) 



§59.— FIRST EXAMPLE: SPIROGYRA (continued). 

 SENSITIVE PERIOD.— With regard to their sensitive period 

 (see § 47, second example), the mentioned properties of a 

 Spirogyra (including the egg) may be classified in the following 

 way: — 



(i) The properties length and breadth of the egg (first state of 

 each specimen) reach their final equilibrium (see § 45) within a 

 cell of the mother plant. Their development and, of course, 

 their sensitive period, are arrested when the egg is ripe. Later 

 on they are independent from any external cause (temperature, 

 light, etc.) whatsoever. 



(2) A certain time (period of rest) after the sensitive period 

 of the above properties the sensitive period of the property 

 number of cells is initiated by the first ceU-division. The value 

 of this property depends on the number of cell-divisions. If 

 we suppose that the divisions follow each other regularly, taking 

 place simultaneously in all the cells of a specimen, the property 

 number would pass through the series of values i, 2, 4, 8, 16, 

 32 . . . 2"- The state of equilibrium (definitive number) may 

 be reached sooner or later (in a given species) according to the 

 external agencies which may augment or diminish the number 

 of divisions. Although we have little information about this 

 subject, it may be considered certain that temperature, food 

 and light have an influence. If the cell-divisions are arrested 

 (for instance, by falling off of temperature) in a given specimen 

 when the number 2* = 16 is reached and in a second specimen 

 of the same species when the cells are 2^ = 32 in number, a 



