238 GLOSSARY 



HERMAPHRODITE. An organism with both male and female organs of re- 

 production, or capable of producing both eggs and spermatozoa. 



HETEROZYGOUS. Containing two factors or allelomorphs for the same 

 character in heredity. 



HOLOBLASTIC. Cleavage in which the division planes cut through the entire 

 cell mass. 



HOLOPHYTIC. Like green plants in the manufacture of food. 



HOLOZOIC. Animal-like in mode of nutrition. 



HOMOLOGY. Genetic relation of parts; implies morphological likeness or 

 structural affinity. 



HOMOZYGOUS. In heredity, containing one kind only, of two alternative fac- 

 tors for the same character. 



HORMONE. An internal secretion necessary for the full activity of some 

 organ at a distance. 



HYDROID. Hydra-like, or pertaining to Hydroidea, a group of coelenterates. 



HYDROLYSIS. A form of chemical decomposition by which a compound is 

 resolved into other compounds by taking up the elements of water. 



IMMUNITY. Protection against disease. 



INDUSIUM. Membrane covering a sorus or fruit-dot in ferns. 



INTUSSUSCEPTION. Reception of foreign matter by all parts at once of 

 living matter, leading to interstitial growth as opposed to growth by 

 accretion or addition on the outside. 



IRRITABILITY. The property possessed by all protoplasm of responding 

 to stimuli. 



KARYOKINESIS. The phenomena of nuclear division involving the forma- 

 tion and the division of chromosomes; same as mitosis. 



KATABOLISM. Destructive metabolic processes in the living organism 

 whereby protoplasm and its derivatives are broken down, forming 

 compounds of lower energy potential and transforming stored energy 

 into energy of heat and movem ent. 



LININ. The substance of the nuclear reticulum other than the chromatin. 



MACRONUCLEUS. The larger nucleus of a protozoan cell in which dimorphic 

 nuclei are present. 



MATURATION. The series of processes in the formation of germ cells by 

 which the number of chromosomes is reduced to one-half. 



MEDUSA. A free-swimming, gonad-bearing sexual generation of coelen- 

 terates. 



MERISTEM. Unformed and growing cell tissue found at the ends of young 

 stems, leaves and roots. 



MEROBLASTIC. Applied to eggs in which the division or cleavage planes do 

 not cut through the yolk mass; superficial cleavage. 



MESODERM. The middle germ layer of an animal embryo in the three-layer 

 stage. 



METABOLISM. The aggregate of chemical changes in living organisms 

 involving the building up of protoplasm (anabolism), and the break- 

 ing down of protoplasm (katabolism). 



METAGENESIS. See alternation of generations. 



