220 Observation of the Origin of Varieties. 
are thus 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 Peloria 
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 which 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 Lamarckiana, on the other, thus 
receive a satisfactory explanation. 
21. HERITABLE PELORIAS. 
Pelorias are very rarely met with in nature as a 
specific character. As an instance I may quote Mentha 
aquatica, the apical flowers of which according to SCHIM- 
PER'S discovery are always regular and consequently 
peloric, 1 and the orchid Uropedium Lindenii, which is 
regarded as the peloric form of Cypripedmm caudatnin.- 
*A. BRAUN, Abh. d. Berliner Akad., 1859, p. 112; and DELPINO, 
Mem. R. Instit. di Sci., Bologna, 5 Ser., Vol. I, 1890, p. 269. 
2 A. BROGNIART, Ann. Sc. nat., 3 Ser.l, Vol. XIII, p. 113 (Plate 
2) ; and J. M. JANSE, Maandblad voor Natuurwetenschappen, Vol. 
XIV, No. 3, 1887, p. 29. Uropedium Lindenii appears to be by no 
