Monoicous. Mosses which have the antheridia and archegonia borne on the same plant, but in separate groups.

Monomer. Any molecule that can exist alone or with other similar molecules instead of the normal two.

Monosomic. Abnormal chromosome complement in which one chromosome of the somatic (diploid) set is missing. A type of aneuploidy.

Monotremata. A sub-class of Mammlia, containing the duckbilled platypus and two genera of spiny anteater.

Morph. Any individual variant that constitutes a forma of a polymorphic species.

Morphactins. Group pf synthetic plant growth-regulating compounds, derived from fluorecarboxylic acid, that reduce and modify growth, especially new growth. Internally, orientation of spindle axes of dividing cells is altered.

Morula. (Zool). Embryo during process of cleavage, before blastula stage; consists of a number of blastomeres.

Mosquito. A Dipteran fly that acts as a vector of numerous tropical diseases, such as Malaria and Yellow fever.

Moth. A lepidoteran that is mainly nocturnal, lacks knobbed antennae, and folds its wings flat at rest. The term has no taxonomic status.

Motor. Concerned with stimulation of effector organs. M. cortex. Part of cerebral cortex controlling nerve to striped muscle. M. end plate. End-organ of a motor nerve fibre, on a muscle fibre, consisting of an accumulation of muscle cytoplasm and nuclei, in contact with the nerve fibre branches, and through which its nerve impules stimulates the muscle fibre. M. nerve.