GLOSSARY 403 



Sex-linked (seJsf;' linkt'). Associated with sex; said of hereditary characters that are 

 inherited unequally by the two sexes. 



Sexual {seks' u al). Involving the production of true germ cells, or the fusion of nu- 

 clei; said of reproduction, or of an individual employing such a mode of reproduc- 

 tion. 



Sexual selection {seks' u al se leV shun). The supposed preference of animals of one 

 sex for certain qualities in the other sex, leading to the preservation of those quali- 

 ties in later generations. 



Shoal (shole) . A shallow place in a body of water; also a sandbank or bar which makes 



the water shallow. 

 Siagonodon {si' a gon' o don). A genus of snakes. 

 Silica {siV ika). Silicon dioxide, the material of common quartz. 

 Silurian {si lu' ri an). Of middle Paleozoic time, between Ordovician and Devonian. 

 Siphon (si' fon). A passageway for currents of water; as the clefts between the 



halves of the mantle of mussels where the edges do not meet, or the tube on the 



ventral side of a squid or cuttlefish. 



Siphonophora {si' fo nof o ra) . An order of Hydrozoa (Coelenterata), the members 

 of which form highly polymorphic colonies {e.g., Physalia, the Portuguese man-of- 

 war). 



Siphonops {si' fo nops). A genus of coecilians (Apoda, Amphibia). 



Siren (si' ren). A genus of salamanders. 



Sistrurus {sis iru' rus). A genus of snakes; the massasauga. 



Slime tube (slime' tube'). A sheath of mucous material secreted on the surface of an 

 earthworm at the time of mating. 



Small intestine (smawl' in fes' tin). That part of the intestine of vertebrates imme- 

 diately following the stomach, as distinguished from the large intestine. 



Smooth muscle (smooth). Muscle composed of non-striated, uninucleate, spindle- 

 shaped cells. It is common in the intestine, bladder and glands of vertebrates. 



Solanum (so la' num). A genus of plants including the common potato, nightshade, 



and many others. 

 Solen (so' len). A genus of razor-shell clams. 

 Solute (so lute'). A dissolved substance. 



Solution (so lu' shun) . A liquid containing another substance in the form of particles 

 not greater than molecules in size. 



Solvent (sol' vent). A liquid in which another substance is, or may be, dissolved. 

 Somatic (somat' ik). Pertaining to the body; when apphed to cells, referring to the 

 sterile body cells in contrast to the germ cells which are reproductive. 



Somite (so' mite). One of the segments into which the body of a worm or arthropod 

 or other segmented animal is divided. 



Spallanzani, Lazaro (spahl' lahn dzah' ne). Italian naturalist and physiologist, 

 1729-1799. 



Specialization (spesh' ali za' shun). Emphasis upon one or a few functions, though 

 not necessarily to the exclusion of others. 



Species (spc' sheez) (pi., species). A group of animals or plants so nearly alike that, 

 in general, they might have sprung from the same parents. (The term is rather 

 arbitrarily used, however). 



Specific (spe sij' ik). Pertaining to a species. 



Sperm (sperm). One of the male germ cells in an animal or plant. 



