586 Species According to the Theory of Mutation. 
course, any given monohybridic cross can only belong 
to one of these two groups. If it is bi-sexual and be- 
haves in a Mendelian fashion we may immediately infer 
that the two parents are to be considered as varieties. 1 
If it is uni-sexual they are elementary species, of which 
the one must have been derived from the other. 
The di-polyhybrids are mongrels whose parents differ 
from one another in respect of two or more elementary 
characters. Two cases must be distinguished. Let us 
confine ourselves first to the dihybrids. In some cases 
/ 
the two points of difference may belong to the same 
category and therefore follow the same laws in the crosses 
and their products. If each of them, considered by itself, 
would lead to the conclusion that the parents were related 
as varieties, the same conclusion will obviously hold good 
for the combination. So, for instance, is Papaver soinni- 
ferum polycephalnm Danebrog to be regarded as a vari- 
ety ; so also, if it is allowed to judge by analogy, Calliopsis 
tinctoria piimila pur pur ea (Vol. I, p. 197). For the same 
reason the compound colors, which may be split into their 
components by means of crossing and can be recon- 
structed out of these, fall within the category of varietal 
characters. 
Similarly forms, of which one has arisen from the 
other by two successive mutations in the progressive di- 
rection, and whose crosses, therefore, conform to the laws 
of uni-sexual unions, would most certainly have to be re- 
garded as elementary species. 
2 And this independently of the nomenclature chosen. For in- 
stance according to the principles enunciated above, Chelidonium 
lachriatum Mill, will have to be regarded as a variety of C. inajus, 
even when this more convenient name is retained. See Part I, p. 65. 
And from a practical point of view it would be very desirable to drop 
the attempt to correlate the nomenclature with the ever-changing 
systematic conceotions. 
