Consider allowing single cells to be glands

[Clare72]

Mayhew and Merritt, (2013) define the secretory cells of the spermatheca as single cell glands - other cells are part of each gland during development, but these die by apoptosis before eclosion.

This does not fit with the UBERON classification of 'gland'

[Clare72]

UBERON def is:
"An organ that functions as a secretory or excretory organ."

We only seem to have secretory subclasses (Malpighian tubules are not considered to be glands), so we are already not 100% consistent with UBERON.