GLOSSARY 355 



Mesothorax. The middle segment of the thorax of an insect. 



Metabolism. The processes concerned in the building up of protoplasm and its 



destruction. 

 Metamere. One of a series of segments composing the body, as in many worms 



;iii(l in arthropods. 

 Metamorphosis. Change of form or structure, as in the larval, pupal, and imago 



stages of an insect's development. 

 Metaphyta. Plants consisting of many cells; all plants above the Protophyta. 

 Metathorax. The posterior segment of the thorax of an insect. 

 Metazoa. Animals which, in an embryonic condition, possess at least two distinct 



germinal layers; all animals above the Protozoa. 

 Microgamete. The male germ cell consisting of a detached flagelliform process of 



a niirrogametocyte. 

 Microgametocyte. The parent male cell. 



Micron. One thousandth of a millimeter; a unit of microscopic measure. 

 Molting. The shedding of the hair, feathers, or outer layer of the skin, which are 



replaced by new growth. 

 Morphology. The science of the outer form and internal structure of animals and 



l)Iants. 

 Myasis. A disease caused by the presence of the larvte of flies in or on the body. 

 Myiasis. Same as myasis. 

 Myiosis. Same as myasis. 



Ocellus. A small simple eye of many invertebrates. 

 Octopod. Having eight feet, as in adult arachnids. 

 Onchosphere. The tapeworm embryo; the hexacanth. 

 Ookinete. Same as zygote. 

 Oospore. Same as zygote. 

 Operculum. A lid-like process or part. 

 Ovum. An egg cell or egg. 

 Ovigerous. Egg bearing. 

 Oviparous. Producing eggs that hatch after they have passed from the body of the 



l)arent. 

 Oviposition. The laying of eggs, especially applied to insects and arachnids. 

 Ovipositor. A specialized organ, as in certain insects, for depositing eggs. 

 Ovoviviparous. Producing eggs that have a well developed shell or covering, as in 



oviparous animals, but which incubate within the body of the parent. 

 Ovulation. The formation of eggs in the ovary; the discharge of the egg or eggs 



from the ovary. 

 Palpi. Appendages, usually organs of touch or taste, attached to the mouth parts 



of insects and other arthropods. 

 Papilla. A small nipple-like or pimple-like projection. 

 Parasiticide. A remedy that destroys parasites. 

 Parthenogenesis. The production of individuals from ova without fertilization by 



tlic male element. 

 Pedipalpi. Leg-like or pincer-like appendages of arachnids, located on each side of 



the mouth. 

 Phylogenic. Pertaining to the ancestral history of an animal or plant. 

 Phytozoon. A colony of animals resembling a plant. 



