having or forming no placenta, as the marsupials and monotremes. adjective (of monotremes and marsupials) having no placenta aplacental a·pla·cen·tal (ā’plə-sěn’tl) adj. Having no placenta.
- Aplanatic lens
aplanatic lens aplanatic lens n. A lens designed to correct spherical and coma aberration.
free from spherical aberration and coma. Historical Examples A lens in which the spherical aberration is corrected is said to be aplanatic. An Elementary Text-book of the Microscope John William Griffith aplanatic triplets 64-68 can only be used on stands with rack and pinion adjustment. Microscopes and Accessory Apparatus Ernst Leitz adjective (of a lens […]
a nonmotile gamete.