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which unite, making a tube (the medullary canal) from which the brain and spinal cord are developed. -- Medullary rays (Bot.), the rays of cellular tissue seen in a transverse section of exogenous wood, which pass from the pith to the bark. -- Medullary sheath (Anat.), the layer of white semifluid substance (myelin),…

A larva, in a stage following the zoëa, in the development of most crabs. In this stage the legs and abdominal appendages have appeared, the abdomen is relatively long, and the eyes are large. Also used adjectively.

An indue development of dark-colored pigment in the skin or its appendages; -- the opposite of albinism.

Development of dark-pigmented tumors.

A picture produced by a process in which development after exposure may be deferred indefinitely, so as to permit transportation of exposed plates; also, the process itself.

All that part of the alimentary canal which is developed from the primitive enteron and is lined with hypoblast. It is distinguished from the stomod, a part at the anterior end of the canal, including the cavity of the mouth, and the proctod, a part at the posterior end, which are formed by invagination and are lined w…

The middle one of the three pairs of embryonic renal organs developed in most vertebrates; the Wolffian body.

pecies undergoes in a series of successively produced individuals, extending from the one developed from the ovum to the final perfected individual. Hence, metagenesis involves the production of sexual individuals by nonsexual means, either directly or through intervening sexless generations. Opposed to monogenesis. Se…

A change in the form or function of a living organism, by a natural process of growth or development; as, the metamorphosis of the yolk into the embryo, of a tadpole into a frog, or of a bud into a blossom. Especially, that form of sexual reproduction in which an embryo undergoes a series of marked changes of external…

The most posterior of the three pairs of embryonic renal organs developed in many vertebrates.

cells, which are metamorphosed into the tissues of the body. A central cavity is commonly developed, and the cells around it are at first arranged in two layers, -- the ectoderm and endoderm. The group comprises nearly all animals except the Protozoa.

Orderly arrangement, elucidation, development, or classification; clear and lucid exhibition; systematic arrangement peculiar to an individual. Though this be madness, yet there's method in it. Shak. All method is a rational progress, a progress toward an end. Sir W. Hamilton.

A whitish soluble powder used as a developer in photography. Chemically, it is the sulphate of methyl-p-amino-m-cresol.

An unnatural smallness of the eyes, occurring as the result of disease or of imperfect development.

, with most of the organs and parts paired, but not repeated longitudinally. Most of them develop a mantle, which incloses either a branchial or a pulmonary cavity. They are generally more or less covered and protected by a calcareous shell, which may be univalve, bivalve, or multivalve.

Having only one axis; developing along a single line or plane; as, monaxial development.

A germ in that stage of development in which its form is simply that of a non-nucleated mass of protoplasm. It precedes the one- celled germ. So called from its likeness to a moner. Haeckel.

Oneness of origin; esp. (Biol.), development of all beings in the universe from a single cell; -- opposed to polygenesis. Called also monism. Dana. Haeckel.

Producing only one kind of germs, or young; developing only in one way.

Having but a single form; retaining the same form throughout the various stages of development; of the same or of an essentially similar type of structure; -- opposed to dimorphic, trimorphic, and polymorphic.