220 Ohscrz'ation of the Origin of Varieties. 



are tliiis to be explained. The explanation is so simple 

 that it follows directly from the preceding discussion. 

 It is merely necessary to point out that the most impor- 

 tant condition for a character to become latent is its pres- 

 ence; and this explains how it is possible that the Pcloria 

 so often appears over the whole area of distribution of 

 the species. Neither a premutation nor a period of muta- 

 tion is necessary for such an occurrence. 



If the loss or latency (for the inner potentiality is ob- 

 viously not lost but only becomes inactive) affects single 

 flowers we have a partial atavism, but if it affects the 

 whole plant we have the complete and heritable Peloria. 



It is on this basis that the atavistic phenomena of the 

 striped flowers, of the many-spiked Plantago (§17, p. 

 148) and of the peloric Linaria fall in line. They are 

 retrogressive phenomena, reversions to ancient charac- 

 ters wdiich have externally become lost but are still pres- 

 ent in a latent state. Their agreement with one another 

 on the one hand, and their contrast with the progressive 

 mutations of Oenothera Laniarckiana, on the other, thus 

 receive a satisfactory explanation. 



§21. HERITABLE PELORTAS. 



Pelorias are very rarely met with in nature as a 

 specific character. As an instance I may quote Mentha 

 aqiiatica, the apical flowers of which according to Schim- 

 per's discovery are always regular and consequently 

 peloric,^ and the orchid Uropediinn Lindenii, which is 

 regarded as the peloric form of Cypripedinni caudatuinr 



^ A. Braun, Ahh. d. Berliner Akad., 1859, p 112; and Delpino, 

 Mem. R. Instit. di Sci., Bologna, 5 Ser., Vol. I, 1890, p. 269. 



''A. Brogniart, Ann. Sc. naf., 3 Ser.l, Vol. XIII, p. 113 (Plate 

 2) ; and J. M. Janse, Maandblad voor N atuurwetenschap p en , Vol. 

 XIV, No. 3, 1887, p. 29. Uroped'mm Lindenii appears to be by no 



