FIGURE 29.9
Cnidocytes of cnidarians. Each cnidocyte contains a stinging capsule, the nematocyst, which itself contains an inverted threadlike weapon. When a “trigger” is stimulated by touch or by certain chemicals, the thread shoots out from the nematocyst. Some of the threads are long and entangle the appendages of small animals that bump into the tentacles. Other threads puncture the prey and inject a poison that paralyzes the victim.