Of the harmonious phenomena in nature it is indeed difficult to find other examples so perfect as those of the habits of these fossorial wasps, or of the mechanism for the fertilisation of orchids. These harmonies in nature are constantly met with in the world of living beings, and it is not astonishing that they have for a long time attracted the attention of many observers and philosophers. As it seemed impossible to attribute them to the organisms themselves, because of the low rank and lack of intelligence of these, it has seemed only natural to set them down as a manifestation of a superior force which organises and directs all natural phenomena. This argument, however, omits one side of the medal. Any close investigation of organisation and life reveals that, beside many most perfect harmonies, there are facts which prove the existence of incomplete harmony or even absolute disharmony. The examination of the flowers of orchids would lead one to the belief that each part, even the smallest and apparently most insignificant, has its _rôle_ in the mechanism for fertilisation and cross-fertilisation. In reality it is not so. There are in certain orchids organs which do not fulfil any function. Even among the species of _Catasetum_, in which the pollinia are thrown with force on the bodies of insects, there are some female flowers in which the male organs are rudimentary and without utility. In these flowers, according to Darwin,[36] “the two membranous sacks containing the rudimentary pollen-masses never open, but they easily separate from each other and from the anther. The tissue of which they are formed is thick and pulpy. Like most rudimentary parts, the pollen-masses vary much in size and form; they are only about one-tenth of the bulk of those of the male.” There are then, without doubt, some structures that are of no service. The existence of these rudimentary pollinia, incapable of being transported or of fertilising the female element, is easily explained by the supposition that formerly the flowers of the _Catasetum_ were true hermaphrodites, but that in the course of time the male organs have become incompletely atrophied in certain flowers, in which, on the other hand, the female part has increased. The occurrence of an actual degeneration is shown by the existence of rudiments of the pollinia too insignificant to accomplish their normal functions. Rudimentary and useless organs are widely distributed, and we find them in many places. Familiar instances are the atrophied eyes of animals that live in the dark, and the sometimes rudimentary sexual organs of many plants and animals.