The fungus also produces pyomelanin, a brown diffusible pigment. Large colonies are observed along with a brown diffusible pigment within two to four days. Plasmodesmata usually only allow the passage of small diffusible molecules, such as various metabolites. This diffusible factor was later shown to be Sonic hedgehog. These changes arise due to diffusible signalling factor encoded by "S. maltophilia". He called the diffusible solutes crystalloids and those that would not pass the membrane colloids. Human shugoshin is diffusible and mediates formation of kinetochore-microtubules during bipolar spindle assembly.