Aplysia californica is the marine mollusk model system Kandel, Dash, and Hochner used for the experiments discussed in this paper. Aplysia has a number of characteristics that make it suitable for neuroscience experiments. The number of cells in the nervous system is small, which makes the organism a tractable one for beginning experiments in a particular research area. The neurons of Aplysia are relatively large and can be cultured, which was likely important for the sensory - motor neuron culture system in which Kandel et al. injected CRE oligonucleotides into individual neurons. Lastly, although Aplysia is a simple sea creature, it has learning modifiable behaviors that correspond to specific neural circuits. Kandel et al. exploited this fact in many experiments by using the gill withdrawal reflex as a behavior in Aplysia that can be modified by learning. (2).