656 ZOOLOGY. 
of northern forms, and alpine ‘‘ species ’’ proving to be va-. 
rieties or seasonal forms of lowland species. For example, 
Weismann states that the European butterflies, Lycaon amyn- 
tas and polysperchon, are respectively summer and spring 
broods. <Anthocharis Simplonica is an alpine winter form of 
Anthocharis Belia, as is Pieris bryonie of Pieris napi. In 
this country, as Edwards has shown, two of the polymorphic 
forms of Papilio Ajax—i.e., Walshii and Telamonides—come 
from winter chrysalids, and P. marcellus from a second 
brood of summer chrysalids. It thus appears that poly- 
morphism is intimately connected with the origin of species. 
Perhaps the most remarkable case of polymorphism is to be 
seen in the white ants (Termites), where in one genus there 
are two sorts of workers, two sorts of soldiers, and two kinds 
of males and females, making eight sorts of individuals ; in 
the other genera there are six. Among true ants there are, 
besides the ordinary males, females, and workers, large- 
headed workers. In the honey-ant (Myrmecocystus Mexi- 
canus), besides the usual workers, there are those with 
enormous abdomens filled with honey. Other insects, es- 
pecially certain grasshoppers, are dimorphic. Certain par- 
asitic Nematode worms are dimorphic; and among the 
Ceelenterates, especially the Hydroids, there is a strong ten- 
dency to polymorphism. 
Individuality.—Perfect individuality among animals is 
the rule, each individual being capable of maintaining an 
independent existence ; but we have seen that there are many 
of the lower animals in which it is difficult to determine 
whether the different members of a colony are really in- 
dividuals or simply individualized organs. 
The student, in referring back to the account of the Por- 
tuguese man-of-war, will find it difficult to say whether the 
four kinds of members of the floating colony are organs or 
individuals, and he will probably agree with the view that 
it is best to provisionally call them zoozds or individualized 
organs ; for the feeders, the reproductive zooids, the digest- 
ive zooids, and the swimming float, or the swimming bells 
ct the other Siphonophores, are highly specialized organs, 
and only differ from true individuals in lacking the power 
