Glossary 



381 



centered can be said to have 

 been solved. 



Epimorpiiosis. The mode of re- 

 generation of organisms in 

 which a multiplication of cells 

 on the surface of injury is first 

 produced, then from tliis ''em- 

 bryonal tissue," the new organ 

 or part is formed; contrasting 

 with morphahwis, a mode of 

 new formation which consists in 

 a direct transformation of an 

 already existing part into the 

 new part. 



Factor (in Genetics). A hypo- 

 thetical unit of structure or of 

 chemical composition, containeJ 

 in the germ-cell, which in some 

 way is held to condition the de- 

 velopment of a particuhir char- 

 acter in the adult, or of a com- 

 plex of characters which are 

 transmitted in constant associa- 

 tion with one another. Factors 

 are believed to interact with one 

 another in development, and at 

 times to be so "linked" that they 

 are only partially independent in 

 transmission. 



Flagellum. a lash-like appen- 

 dage or large cilium serving as 

 an organ of locomotion in some 

 Protozoa and some bacteria. 



FoRAMTXiFERA. A class of rhizo- 

 podous marine Protozoans, usu- 

 ally having a porous shell. 



Formative Stuffs. Hypothetical 

 substances which are supposed 

 to be formed in one part of an 

 organism and transported to an- 

 otiier part, there to produce, or 

 to influence the production of 

 new organs. For example, sev- 

 eral botanists have supposed that 

 the flower substance of some 

 plants is actually produced in 

 the leaves. 



Gamete. A reproductive cell 

 which unites with another repro- 

 ductive cell to form a zygote. 



Gastrula. That stage of embry- 

 onic development in many ani- 



mals which consists of two germ- 

 layers inclosing a central cavity. 

 It is produced from the blastuli 

 (which see) by liic in-sinking of 

 one-half of this into the other. 



Gemmiparois. Producing pcnnnu', 

 or buds (reproducing by bud- 

 ding), aiiplical)le to botli plants 

 and many animals. 



Gemmule. In the origind anJ 

 ]iroper sense a small aggregation 

 of cells set apart in the tissues 

 of some plants aiul animals, 

 notably in many sponges, for the 

 puri)Ose of reproduction. In ori- 

 gin and structure gcmnnilcs arc 

 more like brds than eggs, 

 thouf.'h the end served is very 

 similar to tliat st-rved by sercU. 

 In a secondary and wlinlly hyjio- 

 theti^al sense, gennnules are 

 imaginary, minute bodies given 

 off by ail the tissue ceils of an 

 organism and assembled in the 

 germ cells, there to cause the 

 development of the next genera- 

 tion. This taking of a very con- 

 crete name from botany and 

 zoology, and using it in a wliolly 

 imaginary way to explain hered- 

 itary development was due orig- 

 inally to Charles Darwin, but 

 with more or less unimportant 

 variations of meaning has since 

 iieen resorted to by many of the 

 best known biologists. 

 This exami)le indicates the great 

 importance for biolog)-, espe- 

 cially for the biology of rrpro- 

 duction aiul develo|>ment, of dis- 

 tinguishing betwct-n the same 

 terms used in a strictly objective 

 and descrij^tive sense on the (»ne 

 hand, and in hypothetical, or 

 pure!v imairinar\' sense on the 

 other. 



Gene. A term much used in prrs- 

 ent-dnv gen<>tic.il science, but ap- 

 |>arenlly not differing in any sig- 

 nificiuit particular from factor 

 (which see). 



Genetic. Pertaining to gt-mtics. 



