GLOSSARY-INDEX 419 



sexual stage. The stage in a metamorphosis in which sexual organs are 

 produced. 



shell, of an egg, 250. 



shoulder girdle, 181. 



sieve cells. Large vessels in plants, with perforated partitions separating 

 them from each other, 106. 



sinus. -Any irregular space or dilated blood vessel. 



skeleton, 139, 176. 



skin, 35, 176. 



skull, 180. 



sleep of plants, 137. 



smell. See olfactory organs. 



sociology (Lat. sodus = a companion + Gr. -logia). The study of the 

 relations of organisms in forming societies, 20. 



somaplasm (Gr. soma = body + plasma = substance). The bit of the 

 germ substance in the egg that is set aside in the developing egg to give 

 rise to the new individual, 332. 



somatic (Gr. soma = body) . Pertaining to the body. 



sorus (plural, son). A cluster of sporangia in the leaf of a fern, 269. 



SPALANZANI, 13. 



special creation theory, 350. 



specialization. Adaptation to some special function. 



species. The name given to a group of organisms essentially alike, 370. 



sperms. The male cells in sexual reproduction, 250, 255, 267. 



spermaphytes. Seed-bearing plants, phanerogams, 376. 



spermaries. The glands that produce the sperms, 164, 199, 250. 



spermatocyte (Gr. sperma = seed -\-cytos = cell). A cell in the spermary 

 that is to break up to form sperms, 254. 



spennatogenesis (Gr. sperma = seed + genesis = creation). The devel- 

 opment of the sperms, 254. 



spennatozoids. 'A name sometimes given to the motile sperm-cells of 

 plants, 271. 



spinal cord. The part of the central nervous system of vertebrates extend- 

 ing through the spinal column, 193. 



spinal nerves, 194. 



spindle, 86. 



spiracles. Openings of gill chambers, as in tadpoles; also breathing pores 

 of insects. 



spiral cells. Cells of a fibrovascular bundle with their inner wall thickened 

 to form a spiral thread, 106. 



spireme (Gr. spirema = a coil). A name applied to the chromatin when 

 it forms a thread, prior to division, 85. 



