Amphioxus Touch

Somatosensory system (Wiki) 
This article on the human sensation of touch is provided for reference. 

New perspectives on the evolution of protochordate... (Goog)
    full length PDF: 
p. 6  "Except for surface mechanoreceptors, which make the amphioxus quite sensitive to touch..." 

Basic features of the ancestral chordate brain ... (Goog)   
Amphioxus has direct pathways for activating its locomotory circuits in response to mechanical stimuli via epithelial sensory cells

Lacalli: 2002 
A reexamination of the epithelial sensory cells of amphioxus (Branchiostoma) 
Link to abstract only, but I have PDF & hard copy