From these virtual bionta (parts of the body that may grow into whole organisms) we must distinguish the partial bionta which have not this property. These are separated parts of the body that live for a time after being cut off from the whole organism, but then die off. Thus, for instance, the heart of a tortoise beats for a long time after being cut out. A flower that has been plucked may, if put in water, keep fresh and alive for many days. In some highly organized cephalopods one of the eight arms of the male develops into an independent body, swims about, and accomplishes the fertilization of the female (_hectocotylus_ among the _argonauta_, _philonexis_, etc.). It was at first thought to be an independent animal parasite. The same thing happens with the remarkable foldlike dorsal appendages of a large naked snail (_thetys_), which get detached and creep about. The body of many of the lower animals may be cut in pieces and yet may live for weeks. The life-properties of these partial bionta are important in view of the general question of the nature of life and its apparent unity in most of the higher organisms. As a fact, even here the cells and organs lead their separate individual life, though they are subordinate to and dependent on the whole. It has been attempted to answer this question of organic individuality in the sense of counting all organisms individuals which develop from a single fertilized ovum. Thus, the Italian botanist Gallesio, in 1816, regarded all plants that arise by asexual generation (budding or segmentation)--sprouts, branches, slips, bulbs, etc.--as merely portions of a single individual that came from an egg (the seed). So also Huxley, in 1855, considered the sum of all the animals that have been produced by asexual propagation, but from a single sexually generated animal, to be parts of one individual. In practice, however, this principle is useless. We should have to say that the millions of plant-lice which arise parthenogenetically from unfertilized germ-cells, but are originally descended from one impregnated ovum, are one single individual; so also all the weeping-willows in Europe, because they all came from shoots of one single sexually-produced tree.