On 16w20a there were new spawn eggs
Link: https://gyazo.com/06b3bb06face752766e7f65c7fe238f0

but then the Minecraft 1.10 Pre-Release 2 they were removed
Link: https://gyazo.com/e5836d3d09c8a2c04f2bcca7251250d7

Following steps to find this issue
1. Load up 16w20a or 16w21b or Minecraft 1.10 Pre-Release 1 and look at the creative menu where it says Miscellaneous (lava bucket), then scroll down to look

2. once that's done go to minecraft 1.10 pre-release 2 and check there again