Answer for the main questions of "The Geometer of Race"

a) What is Gould mainly trying to say through Blumenbach's example?

In my opinion, what the author wanted to say by using Blumenbach's example is that whatever significant, innovative or good-intended ideas are greatly influenced by social background.
Also, he wanted to say that the interpretation of ideas depends on the attitude of the interpreter, which are also influenced by social background and may lead to misunderstanding. (In this text, the interpreters are the scientists, who adopted the myth that theories arise only be observation, are unaware of their own mental impositions, and cannot understand the deep mental shift included in the Blumenbach's theory.)

b)What do you think about his argument? What parts are useful or meaningful?What parts are weak or need development?

Almost all his argument was interesting for me, especially the explanation of the concept "degeneration". Also, the explanation of the attitude of old science seems very significant not only for today's science but also for ourselves However, I think it is a little illogical that most beautiful people should live closest to human's primal home, which is told in Blumenbach's theory.
So, I think that the reason why Blumenbach reached to think so should be explained more in detail.