576 - Heredity and Evolution 



trap the prey; Didinium (Fig. 32-4) uses a 

 pointed drill to pierce and kill other micro- 

 scopic animals; and Suctoria (Fig. 30-3) catch 

 and hold their prey with tentacles tipped by 

 suction discs. Multicellular animals also dis- 

 play a bizarre variety of offensive devices. 

 These include stinging organs (jellyfish, bees, 



Fig. 30-3. This one-celled animal, a suctorian, uses its 

 two batteries of tentacles to catch, hold, and pene- 

 trate into other Protozoa. Then it "sucks out" the 

 protoplasm from the victim. Photograph of a glass 

 model of Tokophrya cyclopum. Note the nucleus (dark, 

 oval, left), an internal reproductive bud (center), and 

 a rounded mass of semidigested food (right). (Courtesy 

 of the American Museum of Natural History, New York.) 



wasps, spiders, scorpions, etc.); webs for en- 

 snarement (spiders, etc.); claws for catching, 

 holding, or tearing victims (eagles, lions, 

 tigers, etc.); and teeth for tearing flesh and 

 crunching bone (carnivorous mammals). 



Defensive devices are also widespread in 

 nature. Ciliates often possess trichocysts, 

 which may be used in warding off attack; and 

 many animals possess shells, scales, and other 

 types of armor (Fig. 30-4). There are numer- 

 ous other protective devices of greater or 

 lesser importance. These include many fa- 

 miliar examples — such as spines (cactus, 

 roses, and porcupines); poisonous secretions 

 (numerous plants and animals); unpleasa?it 

 tastes and odors (many plants, caterpillars, 

 and toads); and last but not least, protective 

 mimicry (Fig. 30-5) and protective coloration 

 (many insects and other animals). Also there 

 are many less familiar defensive adaptations, 

 such as the in); sac of the octopus. This con- 

 tractile reservoir is able to eject such a dense 

 cloud of inky fluid that an enemy has diffi- 

 culty finding its intended victim in the dark- 

 ened sea. 



Parasitism. Practically every plant and ani- 

 mal serves as host to one or more parasitic 

 species. Moreover, the association between 

 host and parasite often extends far back into 

 the evolutionary history of the species; and 

 a high degree of specificity may develop 



Fig. 30-4. Female box turtle (Cistudo 

 Carolina) with egg. (Courtesy of the 

 American Museum of Natural History, 

 New York.) 



