In support of my view, I must recall the small forms of Siphonophora known as Eudoxia. These are detached pieces of the common trunk which swim freely in the sea and have a remarkable structure (Fig. [24]). Their mobility is due to a bell provided with strong muscular fibres. The bell is a portion of an individual which possesses organs of reproduction but which is devoid of the means to capture or digest food. These two functions are performed by a second individual which is closely united with the first. The nutrient individual has a long tentacle by which the prey is captured, and a capacious stomach in which it is digested. The products of digestion pass by channels into the reproductive individual, carrying as it were a ready-made blood. Eudoxia in fact is a double being composed of an individual incapable of locomotion or of reproduction, but adapted for prehension and digestion, and of a second individual which can reproduce and which is mobile. Eudoxia is an association resembling that of the blind man and the paralytic, in Florian’s fable.
| Fig. 24.—Eudoxia. (After Chun.) | Fig. 25.—Botryllus
colonies. o, mouth ; A, common cloaca. |
Advance in the organisation of social animals is plainly incompatible with complete loss of individuality, and this becomes the more apparent the higher we reach in the scale of life. In the social Ascidians, each member retains all the organs necessary to life. Animals of the genus Botryllus (Fig. [25]), perhaps the most interesting of these Ascidians, occur in the form of circular colonies. The individuals which compose the colony are grouped radially around a common centre which is occupied by the cloaca. Each individual has its own mouth and digestive tube, but the latter opens into a cloaca, common to all the individuals, by which the excreta are voided. There is, in fact, a single anus, as in the case of Rosa and Josepha which I have just mentioned.
II
INSECT SOCIETIES
Social life of insects—Development and preservation of individuality in colonies of insects—Division of labour and sacrifice of individuality in some insects
Hitherto I have dealt with associations of animals the members of which are linked by an actual material bond. In the insect world there are many cases of highly developed colonies. But the organisation of insects is high, and is incompatible with the existence of actual physical connection between the members of the society.
In early stages of the development of the social instinct in bees, fully formed and similar individuals join together with the object of securing the safety of their individual lives. Sometimes they act together to drive away a common enemy, sometimes, as in winter, they cling in a mass to maintain their temperature. In such primitive societies, the young are not reared in common. It is only in much more highly developed colonies, such as those of some bees and wasps, and of ants and termites, that the chief object of the common action is care of the progeny. Such an extreme development of the colony is attained only by sacrificing the individuality of the members. There is a far-reaching division of labour, so that the queens, for instance, are mere machines for laying eggs. In hive-bees the queen can no longer judge of what is good for the colony, her intellectual functions being degenerate. She is enclosed in her cell and supported by the workers, who see in her the future of the race. In times of want the worker-bees sacrifice their own lives and give the queen the last remnants of the food-supply so that she survives them. The males are incomplete individuals and are tolerated only so long as they are required, after which the workers kill them remorselessly.