32 INHERITANCE. Chap. XIII. 



of lesser anomalies are admitted Toy every one to be due to an 

 arrest of development, that is, to the persistence of an embry- 

 onic condition. But many monstrosities cannot be thus 

 explained ; for parts of which no trace can be detected in the 

 embryo, but which occur in other members of the same class 

 of animals occasionally appear, and these may probably with 

 truth be attributed to reversion. As. however, I have treated 

 this subject as fully as I could in my ' Descent of Man ' 

 (chap, i., 2nd edit.), I will not here recur to it. 



When flowers which have normally an irregular structure become 

 regular or peloria, the change is generally looked at by botanists as 

 a return to the primitive state. But Dr. Maxwell Masters, 6S who 

 has ably discussed this subject, remarks that when, for instance, all 

 the sepals of a Tropseolum become green and of the same shape, 

 instead of being coloured with one prolonged into a spur, or when 

 all the petals of a Linaria become simple and regular, such cases 

 may be due merely to an arrest of development ; for in these flowers 

 all the organs during their earliest condition are symmetrical, and, 

 if arrested at this stage of growth, they would not become irregular. 

 If, moreover, the arrest were to take place at a still earlier period 

 of development, the result would be a simple tuft of green leaves ; 

 and no one probably would call this a case of reversion. Dr. Masters 

 designates the cases first alluded to as regular peloria ; and others, 

 in which all the corresponding parts assume a similar form of 

 irregularity, as when all tlie petals in a Linaria become spurred, as 

 irregular peloria. We have no right to attribute these latter cases 

 to reversion, until it can be shown that the parent-form, for instance, 

 of the genus Linaria had had all its petals spurred ; for a chance of 

 this nature might result front the spreading of an anomalous 

 structure, in accordance with the law, to be discussed in a future 

 chapter, of homologous parts tending to vary in the same manner. 

 But as both forms of peloria frequently occur on the same individual 

 plant of the Linaria, 69 they probably stand in some close relation to 

 one another. On the doctrine that peloria is simply the result of an 

 arrest of development, it is difficult to understand how an organ 

 arrested at a very early period of growth should acquire its full 

 functional perfection ; — how a petal, supposed to be thus arrested 

 should acquire its brilliant colours, and serve as an envelope to the 

 flower, or a stamen produce efficient pollen; yet this occurs with 



68 ' Natural Hist. Review,' April. cases, Sitzb. d. k. Akad. d. Wissensch. : 



p. 253. See also his Lecture. Wien. B 1. LX. anl especially Bi. 



Royal Institution, March 16. 1860. LXVL. 1872 p. 125. 



On same subject, see Moquin-Tandon, ° 9 Verlot. • Des Varietes,' 1865, p. 



' Elements de Teratologic.' 1841, pp. 89; Xaulin. 'Nouvelles Archives du 



1 84-. 352 Dr. Peyritsch has collected Museum." torn. i. p 137. 

 a large number of very interesting 



