The chief characteristic of the Diptera is expressed in the name of the Order, since, with the exception of certain aberrant and apterous forms, flies possess but a single pair of membranous wings, which are attached to the meso-thorax.
Between the typical West African chimpanzee and the gorilla there is no difficulty in drawing a distinction; the difficulty comes in when we have to deal with the aberrant races, or species, of chimpanzee, some of which are so gorilla-like that it is by no means easy to determine to which group they really pertain.
A still more aberrant gazelle is a small North-East African species known as the beira (Dorcatragus melanotis), with very short horns, large hoofs and a general appearance recalling that of some of the members of the subfamily Neotraginae, although in other respects gazelle-like.
Mitsukuri, " On the Structure and Significance of some aberrant forms of Lamellibranchiate Gills," Quart.
TARSIER, the Anglicized form of the scientific name of a small and aberrant lemur-like animal, Tarsius spectrum, inhabiting the Malay Peninsula and islands, and typifying a family.
(b) Tentacles capitate, simple; type of Coryne and Syncoryne; Myriothela is an aberrant form with some of the tentacles modified as " claspers " to hold the ova.
This order can be traced with certainty back to the early Jurassic epoch, while the Permian fossil Eugereon, and the living order - specially modified in many respects - of the Thysanoptera indicate steps by which the aberrant suctorial and piercing mouth of the Hemiptera may have been developed from the biting mouth of primitive Isopteroids, by the elongation of some parts and the suppression of others.
All the well-known breeds of dogs are highly artificial and their maintenance requires the constant care of the breeder in mating, and in rejecting aberrant progeny.
MARSUPIAL MOLE (Notoryctes typhlops), the "Ur-quamata" of the natives, an aberrant polyprotodont from central South Australia, constituting a family (Notoryctidae).
The most aberrant type of larva is that of the genus Prosopistoma, which was originally described as an entomostracous crustacean on account of the presence of a large carapace overlapping the greater part of the body.
The first of these aberrant types is Schweinfurth's chimpanzee (Anthropopithecus troglodytes schweinfurthi), which inhabits the Niam-Niam country, and, although evidently belonging to the same species as the typical race, exhibits certain gorilla-like features.
The skull is narrower and longer than in typical squirrels, and there are distinctive features in the cheek-teeth; but the more aberrant types come much closer to squirrels.
It must, however, be borne in mind that a Trematode may develop in an "aberrant" manner in one host and "normally" in another; and unless we knew the initial stock, the two forms would be regarded as distinct species,.
While establishing the historic divisions of the Silurian in Bohemia, Barrande also propounded his famous theory of " colonies," by which he attempted to explain the aberrant occurrence of strata containing animals of a more advanced stage among strata containing earlier and more primitive faunas; his assumption was that the second fauna had migrated from an unknown neighbouring region.
He has applied the theory with especial ingenuity to the interpretation of the circular bony plates in the carapace of the aberrant leather-back sea-turtles (Sphargidae) by prefacing an initial land phase, in which the typical armature of land tortoises was acquired, a first marine or pelagic phase, in which this armature was lost, a third littoral or seashore phase, in which a new polygonal armature was acquired, and a fourth resumed or secondary marine phase, in which this polygonal armature began to degenerate.
A few are sapropelic, haunting the looser debris that forms the uppermost layer of the bottom ooze of quiet waters: we may cite the aberrant Floscularian Atrochus.
In the article Ibex mention is made of the Caucasus ibex, or tur, C. caucasica, as an aberrant member of that group; but beside this animal the Caucasus is the home of another very remarkable goat, or tur, known as C. pallasi.
SPRINGBUCK, or Springbok (Antidorcas euchore), an aberrant South African gazelle inhabiting the country south of the Zambezi, but ranging north-westwards to Mossamedes.
Special interest attaches to the most aberrant member of the family, the Peruvian Dinomys, known for more than thirty years only by a single specimen taken in a house in Lima, and only lately rediscovered.
Again, while Conjugatae may be shut out from Chlorophyceae as an independent group co-ordinate with them in rank, the Characeae constitute so aberrant a group that it has even been proposed to raise them as Charophyta to the dignity of a main division co-ordinate with Thallophyta.
The Ctenophora are so aberrant in structure that it has been proposed to separate them from the Coelentera altogether: they are, however, theoretically deducible from an ancestor common to other Coelentera, but their extreme specialization precludes the idea of any close relationship with the rest.
As regards existing forms of life, the limitations of the class are perfectly well defined and easy of recognition; for although certain groups (not, by the way, whales, which, although excluded in popular estimation from the class, are in all essential respects typical mammals) are exceedingly aberrant, and present structural features connecting them with the lower vertebrate classes, yet they are by common consent retained in the class to which they are obviously most nearly affiliated by their preponderating characteristics.
The civet-tribe (Viverridae), on the other hand, which is exclusively an Old World group, is abundant in Madagascar, where it is represented by peculiar and aberrant types.
The muscles of the fore limbs are most aberrant, but at the same time more uniformly developed than those of the hinder extremities.
The discoveries of the separate paths of sensory and motor impulses in the spinal cord, and consequently of the laws of reflex action, by Charles Bell and Marshall Hall respectively, in their illumination of the phenomena of nervous function, may be compared with the discovery in the region of the vascular system of the circulation of the blood; for therein a key to large classes of normal and aberrant functions and a fertile principle of interpretation were obtained.
The constituents of the last have often been classed as Copepoda, and among the Branchiopods must be regarded as aberrant, since the "branchial tail " implied in the name has no feet, and the actual feet are by no means obviously branchial.
GERENUK, the Somali name of a long-necked aberrant gazelle, commonly known as Waller's gazelle (Lithocranius walleri), and ranging from Somaliland to Kilimanjaro.
The most aberrant of the true jays is G.
With the exception of the Cetacea, most of the Edentata, and the Sirenia, in which the teeth, when present, have been specialized in a retrograde or aberrant manner, the placental mammals as a whole have a dentition conforming more or less closely to the foregoing type.
The occurrence of one aberrant group (Solenodon) in the West Indies is, however, noteworthy.
The jerboa group (Dipodidae, or Jaculidae) is also mainly an Old World type, although its aberrant representatives the jumping-mice (Zapus) have effected an entrance into Arctic North America.
Zelinkia and Philosyrtis are two slightly aberrant forms described by Giard from certain diatomaceous sands.
Very different, on the other hand, is the condition of things in Australia and Papua, where marsupials (and monotremes) are the dominant forms of mammalian life, the placentals being represented (apart from bats, which are mainly of an Asiatic type) only by a number of more or less aberrant rodents belonging to the mouse-tribe, and in Australia by the dingo, or native dog, and in New Guinea by a wild pig.
Eyestalks and the antennules in this aberrant group correspond to the primitive head somites or not, their distinctness is certainly a secondarily acquired character, for it is not found in the larvae, nor in any of the more primitive groups of Malacostraca.
In the Malacostraca, an elongated heart with numerous segmentally arranged ostia is found only in the aberrant group of Stomatopoda and in the transitional Phyllocarida.
Two other genera, Helictis, an aberrant badger,.
And linsang, an aberrant civet, are representatives of Malayan types.
But it varies much in form and scaling, and some most aberrant varieties have been fixed by artificial selection, the principal being the king-carp or mirror-carp, in which the scales are enlarged and reduced in number, forming more or less regular longitudinal series on the sides, and the leather-carp, in which the scales have all but disappeared, the fish being covered with a thick, leathery skin.