828 GLOSSARY 



ment. They are generally known under the denomina- 

 nation of "shell-lish" ; the cuttle-lish, and the common 

 snails, wlielks, oysters, mussels, and cockles, may serve 

 as examples of them. 



Monocotyledons, or Monocotyledonous Plants. — 

 Plants in which the seed sends up only a single 

 seed-leaf (or cotyledon) ; characterized by the absence 

 of consecutive layers of wood in the stem (endogenous 

 growth), by the veins of the leaves being generally 

 straight, and by the parts of the flowers being gen- 

 erally in multiples of three. {Exarnjiles, Grasses, Lilies, 

 Orchids, Palms, etc.) 



Moraines. — The accumulations of fragments of rock 

 ])rought down by glaciers. 



Morphology. — The law of form or structure independent 

 of function. 



Mysis-stage. — A stage in the development of certain Crus- 

 taceans (Prawns), in which they closely resemble the 

 adults of a genus {Mysis) belonging to a slightly lower 

 group. 



Nascent. — Commencing development. 



Katatory. — Adapted for the purpose of swimming. 



Nauplius-form. — The earliest stage in the development 

 of many Crustacea, especially belonging to the lower 

 groups. In this stage the animal has a short body, with 

 indistinct indications of a division into segments, and 

 three pairs of fringed limbs. This form of the common 

 fresh-water Cyclops was described as a distinct genus 

 under the name of Nauplius. 



Neuration. — The arrangement of the veins or nervures in 

 the wings of Insects. 



Neuters. — Imperfectly developed females of certain social 

 insects (such as Ants and Bees), which perform all the 

 labors of the community. Hence they are also called 

 workers. 



Nictitating Membrane. — A semi-transparent membrane, 



