Species which are uniform in some localities may be polymorphic in others. Such a phenomenon is well exemplified by the orchid _Aceras hircina_. Of this species distinct varieties had previously been known in Germany, but Gallé[9] has lately given a detailed account of a number of most diverse forms found growing in a district of Eastern France. Without reference to his plates it is impossible to give any adequate conception of the profusion of types which the flowers of the species there assume. In some the lip is elongated to many times its usual length, twisting and dividing in a fashion suggesting some of the strangest of the Tropical Orchids. In others the labellum and the lateral petals are all comparatively short and wide (Fig. 13). Intermediates, combining these qualities in various degrees, were abundant, and the condition of the species, which was the only representative of the genus in the locality, recalls the extreme polymorphism of many of the Noctuid Moths. [Illustration: FIG. 13. Various forms of _Aceras hircina_. (After Gallé.) This figure only shows a few of the more striking forms illustrated in Gallé's plates.] Somewhat comparable variability has been seen in another Orchid genus _Ophrys_. In Great Britain the species _apifera_, _aranifera_ and _muscifera_ though variable are fairly distinct, but Moggridge has published two series of plates[10] showing a very different state of things as regards the _Ophrys_ population of the Riviera. Here the outward diversity is such that the ordinary specific names cannot be applied with any confidence and the limits of the species are quite uncertain. It may well be supposed that these Riviera plants are interbreeding, and indeed we may safely assume that they are. It is, however, to be remembered that Darwin showed _apifera_ in this country to be habitually self-fertilised, so that the different behaviour on the Riviera may itself constitute a local peculiarity. Moreover it is to be gathered from Moggridge's account that in the districts which he examined the condition was not to be described by the statement that our three types were there co-existing and hybridising, but rather we should say that the population was polymorphic, containing these three types amongst others. Conchologists are aware that on the Dogger Bank _Modiola_ attains a size unparalleled elsewhere. The same is true of the sponges _Grantia compressa_ and _Grantia ciliata_ in the estuary of the Orwell.[11] Conversely, as we know so well in the case of Man, dwarf races occur in several special localities. Such examples may be multiplied indefinitely.