This is based on the Add-A-Gram puzzles by wildBillMunson. You need to find a chain of words, such that each next word is an anagram of the previous word plus an additional letter. Each one is a single word, and it must match the part of speech as the clue.

Example: a scratch inside a charge inside jackets; the solution is "rasp", "spark", "parkas".

Initially I wrote two Add-A-Gram puzzles... but in my hurry to post them, it seems I've managed to mix them up, unfortunately. The chains were made separately, each with 12 clues. The clue pairs are in the correct order; the 1-letter words are together, then the 2-letter words, then the 3-letter words, and so on. They must have gotten tangled on the way to the "Ask a Question" page.

Below is the chain for you to solve and split. Can you split it into two chains?

(a person / nothing) inside (a non-person / a non-assent) inside (an evergreen / an age) inside (a gas detector / a dirt deposit) inside (a channel / a rock) inside (an adornment / an array) inside (a devil / a device) inside (a short lesson / a foulmouth) inside (identifiers / an organic compound) inside (a pact / detectors) inside (organelles / a scientist) inside (skeleton seers / a pseudo-scientist)

• This is a lovely variant on the Add-A-Gram. Commented Jan 30, 2017 at 4:26

I think I've got a solution:

                         a person   I   O   nothing
a non-person   IT   NO   a non-assent
an evergreen   TIL   EON   an age
a dirt deposit   LINT   NOSE   a gas detector
a channel   INLET   STONE   a rock
an adornment   TINSEL   TENSOR   an array
a device   UTENSIL   MONSTER   a devil
a foulmouth   INSULTER   SERMONET   a short lesson
identifiers   OUTLINERS   MONOESTER   an organic compound
a pact   RESOLUTION   SONOMETERS   detectors
a scientist   NEUROLOGIST   CENTROSOMES   organelles
a pseudo-scientist   NUMEROLOGIST   OSTEOMANCERS   skeleton seers

Thanks to Neil W, who found the skeleton seers. The last one in was the evergreen.

• You have a disappearing U on the LHS. Commented Jan 30, 2017 at 10:50
• Ah, good catch. That means that the answer is LINT/INLET. Commented Jan 30, 2017 at 11:02
• I had your adornment and device, but couldn't connect them so eventually abandoned it. I think there's something exceedingly obscure we're both missing in a couple places
– Rubio
Commented Jan 30, 2017 at 11:02
• @Rubio: I'm not very happy with Outliners and Resolution, but Neurologist and Numerologist seem too good to abandon. Commented Jan 30, 2017 at 11:05
• skeleton seers must be OSTEOMANCERS Commented Jan 30, 2017 at 11:13

Here's a start:

Nothing in non-assent in age in gas detector in rock in array in devil

O in NO in EON in NOSE in STONE in TENSOR in MONSTER in ...

Person in non-person in evergreen

I in IT (Thanks, Deusovi) in... (maybe FIR is intended and the OP mistook the T for an F?)

• I and IT for the second one.
– Deusovi
Commented Jan 30, 2017 at 4:16

$\small\begin{array}{rrlrl} 1&\text{ I }&\text{ a person }&\text{ nothing }&\text{ O }\\ 2&\text{ IT }&\text{ a non-person }&\text{ a non-assent }&\text{ NO }\\ 3&\text{ }&\text{ an evergreen }&\text{ an age }&\text{ EON }\\ 4&\text{ SILT }&\text{ a dirt deposit }&\text{ a gas detector }&\text{ NOSE }\\ 5&\text{ SPILT }&\text{ a channel }&\text{ a rock }&\text{ STONE }\\ 6&\text{ ?? POSTIL }&\text{ an adornment }&\text{ an array }&\text{ TENSOR }\\ 7&\text{ }&\text{ a device }&\text{ a devil }&\text{ MONSTER }\\ 8&\text{ }&\text{ a foul mouth }&\text{ a short lesson }&\text{ SERMONET }\\ 9&\text{ }&\text{ identifiers }&\text{ an organic compound }&\text{ MONOESTER }\\10&\text{ }&\text{ a pact }&\text{ detectors }&\text{ ONCOMETERS }\\11&\text{ }&\text{ a scientist }&\text{ organelles }&\text{ CENTROSOMES }\\12&\text{ }&\text{ skeleton seers }\leftarrow&?\ \rightarrow\text{ a pseudo-scientist }&\text{ }\\\end{array}$