214 f'MK.M OF ORGANS. 



subsequently became, began by being strictly symme- 

 trical or regular, and that subsequent alterations were 

 produced by inequality of growth or development. 

 The researches of organogenists have, however, dis- 

 pelled this idea of unvarying primordial regularity, by 

 showing that in many cases flowers are irregular from 

 the very first, that some begin by being irregular, and 

 subsequently become regular, and even in some cases 

 resume their original condition during the course of 

 their development.^ Under these circumstances an 

 artificial standard of comparison becomes almost an 

 absolute necessity for the time being. 



Changes of form very generally, but not always, are 

 accompanied with a change in regularity : thus a flower 

 habitually bi-lateral may assume the characters of 

 radiating symmetry and vice versa. Increase or 

 decrease of size very frequently also are co-existent 

 with an alteration in the usual form. 



In the case of the arrangement of organs it is often 

 difficult or impossible, in the present state of our know- 

 ledge, to determine whether a given arrangement is 

 congenital or acquired subsequently to the first de- 

 velopment, whether for instance an isolation of parts 

 be due to primordial separation or to a subsequent dis- 

 union of originally combined organs, see p. 58. With 

 reference to the changes in the form of organs, how- 

 ever, it is in general more easy to ascertain the proxi- 

 mate cause of the appearance, and thus teratological 

 changes of form may be grouped according as they are 

 due to, 1 , arrest of development ; 2, undue or excessive 

 development ; 3, perverted development ; and 4, irre- 

 gular development; hence the use of the following 

 > See Baillon, ' Adansonia,' v, 176. 



