Prolific try-scorer Morton will start on the wing and Wells will wear the number six shirt as the Duchy look at aspiring County Championship players. Rayner and Down are named among the replacements.
With the exception of one player, the entire Cornwall development squad is made up of players plying their trade at clubs between level five and level eight.
It also includes a number of former county under-20 players, including ex-Plymouth Albion youngster Noah Nash, who is one of two Brixham players in the starting line-up.
Morton, Wells, Rayner and Down’s inclusion in the Cornwall Development XV means they will miss Saltash’s Lockie Cup match against Plymouth Argaum on Saturday,
Cornwall Development XV: 15 Ben Guy (Camborne), 14 Pete Mabbett (St Ives), 13 Declan Matthews (Camborne), 12 Andrew Saviour (Penryn), 11 Will Morton (Saltash), 10 Mitch Vague (Penryn), 9 Noah Nash (Brixham), 1 Ethan Patterson (Redruth), 2 Tommy Lee-Southworth (Camborne), 3 Dom Connor (Brixham), 4 Jack Heazelton (Truro), 5 Alex Thornton (Hayle), 6 Lewis Wells (Saltash), 7 Kieran Westlake (Camborne), 8 Joe Wilson (Bude, capt).
Replacements: Kieran Brownfield (Pirates Amateurs), Ryan Rayner (Saltash), Sam Chapman (Wadebridge), Mark Vian (St Austell), Jordan Nicholls (Camborne), Tom Simmons (Falmouth), Dan Jane (St Austell), Cavan Boyer (St Austell), Kieran Down (Saltash), Rhys Brownfield (St Ives).