An embryologist is looking at a cross-section of a mouse embryo. she notices that flanking either side of the neural tube (the rudiment of the spinal cord) are eggplant-shaped structures that contain many cell bodies. these structures are most likely:

The answer is ganglia. As indicated, they house many cell bodies of afferent and efferent neurons. Spinal ganglia are located in the dorsal (that contain cell bodies of afferent neurons) and ventral roots (that house cell body of efferent neurons) of a spinal nerve.