3 8 VARIATION 



homceotic variations, and homoeosis of some sort is a frequent 

 accompaniment of meristic variation in longitudinal series. The 

 best instance of this is found in the petals of flowers which are 

 recognized by botanists as modified leaves, and instances are not 

 rare in which the specimen plainly shows the various transition 

 states from leaf to sepal, sepal to petal, and petal to stamen. 



This tendency of one part to assume the character and dis- 

 charge the functions of a neighboring part is an important phase 

 of variation, throwing much light upon the general subject of 

 development. 



With this introduction the student is prepared for the study of 

 meristic variation somewhat in detail, in which he will find that 

 while each species is built upon its own somewhat peculiar and 

 definite pattern, yet this pattern is subject to many and profound 

 alterations, and the organism is frequently able to exist upon an- 

 other and much-distorted plan, all of which goes far toward enlight- 

 ening the student as to the variations that may be expected in the 

 organic world. Studies in meristic variation are useful to the stu- 

 dent of thremmatology, not so much for their own sake as for the 

 light they shed upon the nature and manner of variation. 



Examples of meristic variation. Examples of meristic varia- 

 tion are to be found at every hand. In the doubling of flowers 

 and the stooling of grain, in increased or reduced numbers of 

 fingers and toes, in the four-leaved clover and the branching 

 habit of many plants, everywhere are seen alterations in the 

 customary plan on which nature. does its work. 



Fortunately an extended and valuable collection of meristic 

 variations, mostly among animals, has been made by Bateson. 1 

 He lists his data under 886 headings, each recording from one 

 to several authentic cases. 



Equally complete data covering plants have not been collected, 

 though it is among plants that meristic variation is most common. 

 Indeed, it is so common and so evident that formal collection is 

 hardly necessary. The student is therefore referred to plant life 

 out of doors and to Bateson's collection for a fuller study of this 

 important subject, a bare outline of which, as a guide, being all 

 that is attempted here. 



1 Bateson, Materials for the Study of Variation [Macmillan & Co., 1894]. 



