IN PLANTS HAVING IRREGULAR COROLLAS. 415 
At this stage it may be well to point out that in the cases 
given no assistance in the interpretations of their completeness 
is to be derived from the suggestion that these variations are 
instances of reversion to an ancestral type. 
To some persons it seems more easy to conceive the occurrence 
of a perfect variation back to an ancestral form than to a form 
which has not occurred in the lineal descent, and Reversion is not 
unfrequently invoked to account for large or complete variations, 
though what help is derived from such an hypothesis is not clear. 
It is likely that the Study of Variation will hereafter lead to and 
necessitate a revision of the whole question of the nature of 
Reversion, but this is no part of our purpose at present. It 
must suffice to show that the hypothesis is inadmissible in most, if 
not all, of the present cases. The reasons for this are two :—(1) 
In the case of Zinaria, Veronica, and Streptocarpus several 
distinct and symmetrical forms have been shown to occur as 
variations. It is practically inconceivable that each of them is 
àn ancestral form, and indeed such a suggestion is almost 
meaningless. Since, for example, the form Veronica No. 2 
closely approaches the usual form of other Scrophulariacea, it 
might reasonably be thought to be a reversion, but the forms 
Nos. 1, 3, & 4 cannot also be reversions. (2) The instances in 
Which the strongest case for the hypothesis of Reversion could 
be made out are probably those of the pelorie Linaria and the 
peloric Streptocarpus. For good reasons we suppose an irregular 
flower to be descended from a regular one; these flowers are regu- 
lar, may not they be ancestral? This is a fair suggestion, but it 
introduces certain difficulties. For the pelorie flower, in each case, 
is achieved not by the production of 5 indifferent petals, but by 
the production of 5 petals each like the normal anterior median 
petal, each having in the one case a nectary, and in the other 
the definite striping. Now the possession of a long spur-like 
nectary is a character of many irregular corollas, and is commonly 
supposed to be one of the essential parts of the mechanism of 
cross-fertilization, and on the ordinary view would be held to have 
been developed in connexion with the irregularity of the corolla 
to attract the insects to the right place, for the presence of spur- 
like nectaries in actinomorphic flowers, as Aquilegia, is exceptional. 
Similarly the striping on the anterior petals of Streptocarpus 
may reasonably be looked on as part of the mechanism for at- 
tracting and guiding insects. Though, therefore, we do not wish 
