284 
Transarfloiift of the Royal Society of South Africa. 
together collective 8|)cr?Vs. The plan followed bv the senior author is to 
bestow the term forma tt/pica on the earliest-described form of these 
" collective species," and that of varietcdes on those described later — a 
necessary concession to the rule of priority in nomenclature, which does not 
affect the philosophical side of the question, since it is mitigated by the 
practice of placing the typical form not necessarily at the head of the series, 
but in any position which expresses the relationship. Thus the forms of 
Bana esculenta are arranged in the following order* : 
1. Raua esculenta, var. ridihuncla, Pall. 
2. ,, var. saliarica, Blgr. 
'J- /. typica. 
4. ,, ,, var. lessonae, Camer. 
5. ,, ,, var. chineusis, Osb. 
In the case of Ayama hispida the typical form would appear last on 
tlie list. 
The general practice among systematists is to call subspecies or varieties 
forms which, however distinct, are known to intergrade. Intergrading is 
of two kinds : 
It may be associated with the known joining of the two respective 
habitats, intermediate specimens inhabiting intermediate disti-icts. Or the 
two habitats do not join, but an examination of a series of specimens will 
show an intergnidation of characters ; the forms are not strictly 
geographical. 
Then, other systematists accord only subspecific rank to forms which, 
though not actually intergrading, differ too slightly from the type to be 
regarded as species ; they do this, to some extent, on the assumption that, 
thougli not known to intergrade, they will be found to do so Avhen larger 
series are examined. The describer's knowledge of the group to which the 
animal or plant belongs justifies him in anticipating the evidence of actual 
intergradation. 
Several modeim authors wish to restrict the subspecies to geographical 
forms. Any ever so slight deviation from the normal, if associated with a 
distinct habitat, becomes a subspecific form, for which the term forma 
vicaria has also been proposed. It seems, however, that it is just in such 
cases that the adjunction of a third name is least wanted, as the indication 
of the locality after tlie name of the species is amply sufficient to avoid 
confusion. 
A considerable degree of differentiation is needed to justify even a 
varietal name, and we should be careful not to overburden nomenclature 
with Latin names ; but when once it is ascertained that strong modifications 
aifect a large proportion of the individuals from a given district, it is 
advisable to express the fact by a name, all the more if the individuals in 
* Cf. Boulenger, Ann. Mag. N.H. (9), ii, 1918, p. 241. 
