294 GLOSSARY 



REVERSION. The reappearance in the offspring of a 

 character proper to a more or less remote ancestor, and not 

 exhibited by the immediate parents. 



ROTIFERS. A kind of minute aquatic animals. 



SEGMENT. One of a series of more or less similar trans- 

 verse divisions. 



SESSILE. Fixed and stationary, but (in the strict sense) 

 without a stalk. 



SOMATIC. Belonging to the body of a zygote. 



SPECIES, LINN^AN. A group of organisms of closely 

 similar appearance. 



SPECIES, JORDAN'S. A group of organisms believed to have 

 arisen by a mutation. (Jordan himself did not, however, 

 suppose so.) 



SPORT. A marked mutation often one occurring under 

 domestication. 



STAMENS. The organs of a flower which bear the pollen. 



STANDARD. The large, upright petal at the back of such 

 a flower as that of the sweet-pea. 



STIGMA. The uppermost part of the pistil, upon which the 

 pollen is received. 



STRATUM. A layer. 



STYLE. A stalk connecting the stigma with the ovary 

 part of the pistil. 



TESTA. The skin or coat covering a seed. 



THRUM-EYED. Having the anthers situated at the throat 

 of the corolla, and the stigma lower down, enclosed in the 

 tube. 



TUBE. The basal tubular portion of a corolla hi which 

 the separate petals are closely fused together, as is the case 

 with that of the primrose. 



UNICELLULAR. Consisting of a single cell. 



VARIATION, CONTINUOUS. See Chapter IV. 

 VARIATION, DISCONTINUOUS. See Chapter V. 



WINGS. The lateral petals of a pea-flower. 



ZOOLOGY. The scientific study of animals. 

 ZYGOTE. The organism produced by the fusion of a pair of 

 gametes. 



