Does a Nintendo DS need to have a Memory stick

No the DS does not require a memory stick. This is mostly due to the fact that DS carts run on flash memory, which means that you'll never have to worry about dying in cartridge batteries. (Remember the old days when you owned an NES or SNES and you played an RPG, put 20+ hours into the game only to find your game save wiped away? Well that was because the save chips were powered by batteries installed in the carts) Flash requires no batteries for saving, whici means the memory is already on the DS carts themselves.