158 THE QUANTITATIVE METHOD IN BIOLOGY 



Remark I. : In Fig. 22 the letters represent specimens of successive 

 age. 



Remark II. : The primordium red is original, arrested, transitory ; the 

 primordiunx blue is metamorphic, arrested, persistent. (See § 46. ) 



Remark III. : The primordia red and blue are two terms of an embryo- 

 logical series. (See § 133.) 



Remark IV. : The possibility of investigating the three primordia (volume, 

 weight precip., colour) in the same mixture is conceivable. This would be 

 realized if we disposed of an acid solution a and an alkaline solution b pro- 

 ducing a precipitate when mixed, in such a way that every excess of a would 

 be indicated by red and vice versa, supposing, moreover, that the total volume 



of the mixture were not modified 

 by the occurring chemical reactions. 

 A chemist could perhaps indicate 

 two substances which would satisfy 

 the required conditions. 



However it may be, the above 

 possibility being admitted, we may 

 look upon the 200 portions (mix- 

 tures) as being specimens of different 

 age of the same species. The three 

 primordia being observed and 

 measured in all the specimens and 

 their curves being constructed, a 

 diagram similar to Fig. 23 would 

 be obtained. 



Since the causes (pipettes A and 

 B) are exactly the same for the 

 three primordia, the curve of each 

 primordium depends on its specific 



Remark V. : Each of the three 

 curves in Fig. 23, considered separ- 

 ately, does not represent the develop- 

 ment of a specimen considered as 

 Fig. 23.— Curves of development of three a whole. This development is a 

 primordia of a mixture of two liquids complex something, the exact in- 

 (see text) — v, curve of growth of the vestigation of which is possible by 

 total volume ; p, curve of growth of measuring the growth of each 

 the weight of the precipitate ; rb, curve primordium separately. In the 

 of development of the colour : r, red leaves of the mosses and other 

 period ; 6, blue period — between both objects I have observed facts which 

 a period of hesitation ; of, duration of recall the above example (gradation 

 the development ; 0, origin curves. Part VIII.). (Compare § 49 : 



application of the quantitative method 

 on embryology. In Fig. 23 the volume is the most convenient leading 

 property.) 



§ 115.— SEVENTEENTH EXAMPLE : AN URN CON- 

 TAINING 100 PRISMS a AND 100 PRISMS b {continued, 

 from § 100) . — An urn contains : 



(i) 100 right prisms a, the base of each being a square of 

 side I cm., the height 2 cm. 



(2) 100 prisms h differing from the prisms a only by their 

 height, which is 3 cm. 



It is obvious that the conditions are the same as if the urn 

 contained 100 white and 100 black balls (see this example in 

 § 98). When the prisms are taken one by one in series of n 

 prisms (each prism being put again into the urn after its height 



