In other orchids (_Catasetum_, Fig. 1), the male elements are discharged by a spring-like arrangement on the body of insects. When certain parts of the flowers are touched, the pollinia are thrown off like arrows, which, in the place of the barbs, have viscid swellings. “The insect, disturbed by so sharp a blow, or after having eaten its fill, flies sooner or later away to a female plant and, whilst standing in the same position as before, the pollen-bearing end of the arrow is inserted into the stigmatic cavity, and a mass of pollen is left on its viscid surface.”[33] After giving detailed descriptions of the cross-fertilisation of flowers by such peculiar means, Darwin makes the following remark: “Who would have been bold enough to have surmised that the propagation of a species depended on so complex, so apparently artificial, and yet so admirable an arrangement?”[34] One orchid (_Herminium monorchis_, Fig. 2), which bears very small flowers, is remarkable for the way in which it is fertilised by insects. Only very small insects are able to penetrate the flowers. The space being very limited these minute insects can enter the flower only in a particular way, and at one of the corners. This causes the pollinia to become attached always to the same place, which is on the outer side of one of the two front legs. When the insect, the carrier of the pollinia, enters a second flower, it can scarcely fail to fertilise the stigma, which is on the corresponding side. Darwin said that it would be difficult to find a case in which there was so marvellously complete an adaptation to a very peculiar mode of fertilisation as the little flower of _Herminium_. [Illustration: FIG. 2.—_Herminium monorchis_ (after Sowerby, “English Botany,” ix. 1869) ] In addition to orchids, there are other flowers the organisation of which is adapted in a remarkable way to fertilisation by insects. But to find perfect harmony in the nature of living beings it is not necessary to confine our observations to flowers. The animal world furnishes us with numerous examples. To avoid going into the details of these, I shall content myself with a description of the most remarkable instances. Every one has seen, flying near the ground, small, slender, and pretty wasps. From time to time these bury themselves in the earth or sand, and re-appear in a few minutes. These are the fossorial wasps, the interesting habits of which have been studied by Mr. J. H. Fabre, of Avignon. They are not gregarious, but lead solitary lives and differ in their habits from their congeners. Bees feed their larvæ with honey and pollen which they take to them during the whole period of their development. Wasps are carnivorous, predatory insects, and bring their spoils to their brood of soft and feeble larvæ which are unable to provide for themselves. Bees and most wasps look after the welfare of their young ones in the fashion of human parents in nurseries.