On the other hand, certain other parts of the hotly, as the result of use, become extraordina rily developed: such are the tactile papilla. of the blindtish. the greatly lengthened feelers and legs. the long. delicate tactile hairs of various crustaeca and insects. It is plainly the case that the enhanced development of these organs is the result of frequent use or exercise. There is no' need of invoking, natural selection. these parts developing as the direct result of the change of habits, of the new needs of the animals to feel their way about, forced to adopt such hab its by the abnormal conditions of their existence. Although the animals are members of very dif ferent groups. inheritin:! very different structures and habits. yet all genuine cave animals resemble each other in being pale, ghost-like, in the ex altation of the tactile sense, and the correspond ing increase in length and delicacy of the ex tremities.
Vet some naturalists of the Neo-Dorwinian school reject. the operation of the Lamarckian factors and illogically attribute the creation of this wonderful assemblage of blind forms to natural selection, and others to painnixia—i.e. the cessation of natural selection.
Balance of Theories.—In his elaborate work on the eyes of blind fishes fully and candidly discusses the conflicting views, and con cludes as follows: "The Lama wkian view, that through disuse the organ is diminished during the life of the individual, in part at least on account of the diminution of the amount of blood going to a resting organ. and that this effect is transmitted to succeedimr generations, not only would theoretically account for unlimited pro gressive degeneration. but is the only view so far
examined that lines not on the face of it present serious objections." It would be a thorough test of the theory of deseent if we could keep these creatures in eon finement, exposed first to twilight and then to the full light el day, and endeavor to 1)11411 a series of generations of these blind animals and ascertain whether their descendants would not revert to their original ancestral eyed forms.
Fortunately. an underground laboratory for the study of cave animals has been established by Vir6 in the old catacombs and underground quarries extending under the Jardin des Plantes, in Paris. liere are all the conditions of a cave, viz. perpetual darkness, an unvarying tempera ture. and running water for aquatic forms. M. Viri• has introduced various blind or eyed spe cies, and eventually we may expect t44 have much light thrown on the interesting problems sug gested by such studies as these.
Great. activity has been shown iu France in the exploration of the caves and subterranean streams of the Midi. A de Spi'dr•ologie has lien orranzied for several years.
Consult: A. S. Packard, The Cave Fauna of North America" (Memoirs National Academy of Vol. VI. many plates. Washington, 1•:+): C. H. Eigenmann, "The Eyes of the Blind Vertebrates of North America" (Archie fiir Entleiekelumamnevhaniks r Organismen, V111., 1811:1) ; and Other papers. See also the writings of Tellkampf, Schi?dte. Cope, Putnam, Garman, Ilenshaw, Joseph, Chilton, and others.