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GLOSSARY 



genesis, origin). The process by which 

 spermatozoa are formed. 

 Sper'ma-to-zo"on (Gr. sperma, seed; zoion, 

 animal). A mature male reproductive 

 cell, spenn. 

 Sphinc'ter ( Gr. sphinggein, to bind tightly ) . 

 A ring-like muscle surrounding a natu- 

 ral orifice; the opening is closed by its 

 contraction. 

 Spic'ule (L. spiciilum, a little point). A 

 sharp, needle-like body, characteristic 

 of sponges. 

 Spi'nal corumn (L. spina, thorn, spine). A 

 continuous series of vertebrae in verte- 

 brates which houses the spinal cord. 

 Spi'nal cord. The tubular part of the cen- 

 tral nervous system which extends pos- 

 teriorly from the brain throughout the 

 length of the spinal column. 

 Spin'dle (A.S. spinnan, to spin). The spin- 

 dle-shaped threads or fibers associated 

 with the chromosomes in mitosis, ra- 

 diating out from the centrosomes. 

 Spi'ra-cle (L. spiractiliini, air hole). A 

 breathins orifice of insects and the 

 first sill slit in cartilisfinous fishes. 

 Spleen (Gr. splen, spleen). A large organ 

 situated in the upper part of the ab- 

 domen on the left side and lateral to 

 the stomach havincr to do with red 

 blood cell disinteo;ration. 

 Spore (Gr. spora, seed). A special encap- 

 sulated reproductive body of one of the 

 lower organisms. 

 Spor'u-la"tion (Gr. spora, seed). Repro- 

 duction by multiple fission, forming 

 spores. 

 Stat'o-cyst (Gr. statos, stationary; kijstis, 

 sac). An organ of equilibrium found 

 in invertebrates. 

 Stat'o-lith (Gr. statos, standing; lithos, 

 stone). The solid body within a stato- 

 cyst. 

 Ste-ap'sin (Gr. stear, tallow; pepsis, di- 

 gest). A pancreatic enzyme which acts 

 upon fats. 

 Ster'num (L. breastbone). Breastbone. 

 Stig'ma (Gr. a pricked mark). A light- 



sensitive pigment spot in certain Pro- 

 tozoa. 

 Stim'u-lus (L. stimidare, to incite). An en- 

 vironmental change which causes a 

 response. 

 Stra'ti-fied (L. stratum, a covering). Ar- 

 ranged in layers. 

 Stri'at-ed (L. stria, channel). Cross-striped, 



such as in skeletal muscle. 

 Sub-cu-ta'ne-ous (L. sub, under; cutis, 

 skin ) . The region immediately beneath 

 the skin. 

 Sub'mu-co"sa (L. sub, under; mucosus, 

 mucus). One of the layers of tissue in 

 the wall of the digestive tract. 

 Su'ture (L. sutura, from suere, sutum, to 

 sew ) . The point of fusion between two 

 bones. 

 Swim'mer-et (A.S. swimman). Paired bira- 

 mous appendage of the crayfish, just 

 posterior to the walking legs. 

 Sym'bi-o"sis (Gr. syn, together; bios, liv- 

 ing). Living together of two species. 

 Sym"me'try (Gr. syn, together; meton, 

 measure). The regular or reversed dis- 

 position of parts around a common 

 axis, or on each side of any plane of 

 the body. 

 Syn'apse (Gr. syn, together; hapto, unite). 

 The region of contact of two adjacent 

 neurons. 

 Syn-ap'sis. Temporary union of maternal 

 and paternal homologous chromosomes 

 prior to the first maturation division. 

 Syn-cyt'i-um ( Gr. sijn, together; kytos, cell ) . 



A multinucleate mass of protoplasm. 

 Sys'tem (Gr. syn, together; histanai, to 

 place). A group of organs having the 

 same general function. 

 Sys'to-le (Gr. syn, with; steUein, to set, 

 place). The contraction phase of the 

 cardiac cycle. 



Tac'tile (L. tangere, to touch). Pertaining 



to the sense of touch. 

 Tax-on'o-my (Gr. taxis, arrangement; no- 



