Glossary. 213 



Hydromedusae. — Also Kydrozoans. Hydroid colonies with special 



sexually reproductive persons, which are often liberated as floating 



bells or discs. 

 Idio-plasm (A and B). — See pp. 31 and 32. 

 Ids. — See p. 123. 



Invertebrata. — Animals with a dorsal heart and without a backbone. 

 Karyokinesis. — The changes which are observed in the nucleus both 



immediately before and after cell division. See Chromatin threads. 

 Lamarckian factors. See Somatogenetic characters. Also Neo- 



Lamarckians. 

 Metaphyta. — Multicellular plants (q. v.). 

 Metazoa. — Multicellular animals (q. v.). 



Micellae (Nageli). — See Molecules, with which they are identical. 

 Microsomata. — The protoplasm of certain vegetable cells is in places 



characterized by the presence of minute corpuscles, which may be 



regarded as part of the protoplasm, and are certainly of a protoplasmic 



nature. These are termed Microsomata. 

 Molecules (Weismann). — See p. 122. 

 Multicellular organisms. — Organisms composed of many cells, as 



distinguished from the Unicellular organisms, where each individual 



is constituted of only one cell. 

 Natural Selection. — Survival of the Fittest in the struggle for 



existence. For a full account of the process see Darwin and after 



Darwin, p. 251 et sea. 

 Neo-Darwinians. — Those who believe that Natural Selection has 



been the only modifying influence in the evolution of species, and 



that the material for its action has been only plasmogenetic 



characters (q. v.). 

 Neo-Lamarckians. — Those who hold that organic evolution has been 



effected solely by means of the occurrence and preservation (inheritance) 



of somatogenetic characters (q. v.). 

 Nuclear Thread or Loops. — See Chromatin threads. 

 Nucleo-plasm. — See pp. 30 and 32. 

 Nucleus. — See Cell nucleus. 

 Nutritive congenital characters. — See p. 64. 

 Ontogenetic grades. — See p. 35. 

 Ontogeny. — The life history of the individual, as distinguished from the 



ancestral history of the race (Phylogeny). 

 Ova. — Eggs — the product of the female reproductive gland (ovary or 



ovarium). 

 Ovule. — The seed in its earliest condition. 



Pangenesis (Darwin). — The theory of Heredity by gemmules (q. v.). 

 Panmixia (Weismann). — The condition ot free intercrossing, i.e. 

 where Natural Selection (q. v.) cannot act. 



