440 APPENDIX 



HAUSTORIA. Sucker-like absorbing organs of parasitic plants; e.g., 

 Dodder. 



HEPATIC PORTAL SYSTEM. Non-oxygenated but food-laden blood 

 from digestive tract to the liver via hepatic portal vein. Oxygen- 

 ated blood reaches liver via hepatic artery. All leaves via 

 hepatic vein. Thus there is a double blood supply to liver in 

 all Vertebrates. 



HEREDITY. The transmission of characters from parent to off- 

 spring through the germ cells. 



HERMAPHRODITE. An organism bearing both male and female 

 reproductive organs; e.g., Hydra and Earthworm. 



HETEROSPORY. The condition of producing two kinds of spores, 

 megaspores and microspores, as in the higher plants. 



HETEROZYGOUS. Producing gametes which fall into two numeri- 

 cally equal classes with respect to the genes (allelomorphs) for a 

 pair of alternative characters. See Homozygous. 



HISTOLOGY. The science which treats of animal and plant tissues. 

 Microscopic anatomy. 



HOLOPHYTIC. Type of nutrition involving photosynthesis. Char- 

 acteristic of green plants. See Holozoic and Saprophytic. 



HOLOZOIC. Type of nutrition involving the ingestion of solid food. 

 Characteristic of animals. See Holophytic and Saprophytic. 



HOMOLOGOUS CHROMOSOMES. The members of a pair of chromo- 

 somes, of a duplex group, one paternal and the other maternal in 

 origin, which bear the same or allelomorphic genes. See Synap- 

 tic Mates. 



HOMOLOGOUS GENES. Genes similarly situated on homologous 

 chromosomes. See Allelomorph. 



HOMOLOGY. Fundamental structural similarity, regardless of func- 

 tion, due to descent from a common form. 



HOMOTHERMAL. Animals provided with a mechanism which main- 

 tains the body at a practically constant temperature, usually 

 higher than that of the environment. E.g., the 'warm-blooded' 

 animals, or Birds and Mammals. 



HOMOZYGOUS. Producing gametes all of which bear the gene for 

 one of a pair of alternative characters. See Heterozygous. 



