http://www.macrumors.com/2015/04/27/os-x-10-10-4-yosemite-beta-2/
Apple today seeded the second beta of OS X 10.10.4 to developers, approximatel
y a week and a half since releasing the first 10.10.4 beta and nearly three we
eks after releasing OS X 10.10.3 with the Photos for OS X app to the public. A
longside the new developer beta, Apple also released the first public beta ver
sion of OS X 10.10.4.
Developers can download the new beta, build 14E11f, through the Software Updat
e mechanism in the Mac App Store or through the Mac Developer Center.
OS X 10.10.3 introduced several consumer-facing changes including the new Phot
os for OS X app, a redesigned emoji picker, new diversified emoji, and more, b
ut OS X 10.10.4 appears to be an under-the-hood update that brings performance
enhancements and bug fixes.
The first two updates to OS X Yosemite, OS X 10.10.1 and OS X 10.10.2 were als
o minor behind-the-scenes updates that improved performance through bug fixes
and enhancements.