When writing your thesis (particularly the literature) it is tempting to include figures from publication or the web
Bear in mind your PhD thesis is effectively a publication of the University of Glasgow and copyright concerns may arise
You should always reference where the figure came from (if its a website, put the URL and the date you accessed it)
If the figure is unaltered then you may need to seek publisher permission
The journal publishers have instructions on their websites or you can use central services like copyright clearance centre or rightslink
the correct wording for the caption is then
'reproduced with permission of AIP publishing' etc
The way you can get round this is to alter the figure. This can be quite minor - altered font, colours, symbols. Then write 'adapted from Ref YY'
It is also tempting to use figures drawn by other group members. If the exact same figure appears in a previous thesis you may be accused of plagarism (!)
Either draw your own figure or write an acknowledging sentence
'figure courtesy of Dr Z'