THE ANT-COLONY AS AN ORGANISM 31% 
destroyed by their own workers. The parasites then proceed to 
lay eggs but these give rise only to males and females as the 
worker caste is entirely suppressed. The colony retains a mixed 
character, the parasitic species usurping the functions of the germ- 
plasm, while the host is purely somatic. As there are no means 
of prolonging the lives of the host-workers and as they do not re- 
produce, the whole colony is short-lived and the maturation of the 
parasitic sexual individuals has to be accelerated so that it will 
fall within the brief life-time of the worker hosts. This condition 
I have called permanent social parasitism. 
These four peculiar types of colony-formation all lead to 
the formation of compound colonial organisms, comparable to 
certain compound personal organisms which, with few exceptions, 
ean be produced only by artificial means. In temporary social 
parasitism the colonial egg can develop its somaonly when grafted 
on to the soma of another species. This soma eventually perishes 
and the colony then assumes a normal complexion. This condi- 
tion reminds us of certain tropical plants, like the species of Clusia 
and Ficus, which develop as epiphytes on other trees but after 
killing their hosts take root in the soil and thenceforth grow as in- 
dependent organisms. The slave-makers of the sanguinea or 
facultative type are also unable to develop the soma except when 
grafted on to the soma of another species, but in this case the co- 
operation of both somas in nourishing and protecting the germ- 
plasm is maintained for a much longer period. This kind of colony 
may be compared with a graft made by uniting the longitudinal 
half of one plant with that of another so that both take nourish- 
ment through their roots. To make the resemblance more com- 
plete one of the grafted halves would have to be pruned in such a 
manner as to prevent flowering. In the amazons or obligatory 
slave-makers and the permanent social parasites the alien soma 
alone has a nutritive function, so that the conditions are like those 
in ordinary vegetable grafts, in which the stock retains the roots 
and the scion produces the flowers and fruit. 
I have dwelt on the various methods of colony formation not 
only because they give us an insight into colonial reproduction, 
but because they throw light on the colonial organism from the 
