RP neurons

[yamaoka kageyuki bun 6631]

Dose anyone out there know what is the origin of the name of Drosophila
embryonic and larval "RP neurons"?
I've retroacted to a paper of Goodman et al. (1984) Science vol. 225, 
but unfortunately I cannot find out THE ORIGIN.

Can anyone give me some informations?
Thanks in advance!!

******* Kageyuki Yamaoka,    e-mail: dros at hakusrv.toyo.ac.jp *******
           Natural Science Lab., Toyo Univ. Asaka Campus
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