GLOSSARY 451 



the Earthworm, which receive the sperm from another worm 

 and retain them until fertilization is to occur. 



SEPAL. A leaf of the calyx of a flower. 



SEPTA. The partitions which divide the coelom of the Earthworm 

 into a series of chambers, or metameres. 



SERIAL HOMOLOGY. Homology of a structure of an organism with 

 another of the same organism; e.g., appendages of the Crayfish, 

 fore- and hind-limbs of Vertebrates. 



SETAE. Bristle-like structures which protrude from the body wall 

 of the Earthworm and aid in locomotion. 



SEX CHROMOSOME. The odd, X, or accessory chromosome which 

 bears the differential gene for sex. 



SEX-LINKED CHARACTERS. Characters represented by genes on 

 the sex chromosomes. 



SHOOT. Stem and leaves as contrasted with the root. 



SIMPLEX CHARACTER. The result of a determiner, or gene, from one 

 parent only. 



SOL. A colloid which is highly fluid. 



SOMA. Body tissue (somatoplasm) in contrast with germinal tissue. 



SPECIAL CREATION. Abandoned doctrine that. each species was 

 specially created. Implies fixity of species. See Evolution. 



SPECIES. In classification, the main subdivision cf a genus. A 

 group of individuals which do not differ from one another in 

 excess of the limits of "individual diversity," actual or as- 

 sumed. 



SPERM. Male gamete. Spermatozoon. 



SPERMATID. Male germ cells after the final maturation division 

 but before assuming the typical form. of the ripe sperm. 



SPERMATOCYTES. Cells arising from the spermatogonia. Primary 

 spermatocyte arises by growth from the last generation of 

 spermatogonia. Primary divides to form two secondary 

 spermatocytes. 



SPERMATOGENESIS. The development of the sperm from a primor- 

 dial germ cell. 



SPERMATOPHYTES. Plants bearing true seeds. Seed Plants. Flow- 

 ering Plants. Phanerogams. 



