196 GLOSSARY 



fluid containing the smaller amount. The same is true of carbon dioxide. 



Respiration is believed to occur in all living organisms. 

 Ro'dent, mammals with curved self-sharpening incisor teeth, order including 



mice, rats, squirrels, rabbits, etc. 

 Ros'trum, a beak-like projection or snout. 

 Ru'mi nant, chewing the cud. 



Sac, a cavity or pouch. 



Sa'crum, a composite bone formed by the union of vertebrae in the region of 

 hips. 



Scap'u la, the shoulder-blade. 



Sep'tum (pi. sep'ta), a wall or partition between two cavities. 



Se'ta (pi. se'tae), small bristles or stiff hairs. 



Sex'u al, pertaining to sex. 



Si'nus ve no'sus, an enlargement of the termination of the large veins. 



Si'phon, a tube-like organ. 



So'mites, the serial segments or rings composing the bodies of many animals. 



Spe'ci es, a word used in classification to designate a group of animals differ- 

 ing only in minor details. 



Sper'ma ry, the organ in which sperm cells are developed. 



Sperm cells, the small, often motile, reproductive cell, which fuses with the 

 egg cell. 



Spic'ules, tiny needles of mineral substance found in the walls of many ani- 

 mals, notably sponges. 



Spi'ra cle, an opening into the tracheal breathing organs of insects. 



Spire, the coiled portion of a gasteropod shell. 



Spore, a cell capable of developing into a new organism. 



Sternum, a bone extending along the lower middle line of the chest region. 



Stom'ach, the region of the alimentary canal especially adapted to digest 

 food. 



Stom'ach-in tes'tine, a region of the alimentary canal adapted to both digest 

 and absorb food. 



Sub cla'vi an, situated beneath the clavicle. 



Su'ture, the junction of two contiguous structures. 



Swim'mer ets, the abdominal appendages in crustaceans. 



Sym bi o'sis, an association of two animals which is mutually helpful. 



Tar'sal, one of the bones of the tarsus or. ankle. 



Tar'sus, (l) the ankle; (2) the fifth or terminal joint in an insect's leg. 

 Ten'ta cles, special organs for touch; also used sometimes for other purposes. 

 Terrifying attitudes, protective attitudes assumed by some animals. 

 Tho'raz, the region of the body between the head and abdomen. 



