"And they came, the men along with the women ('al hanashim), as many as were willing of heart, and brought bracelets, and earrings, and rings…all jewels of gold". Both men and women – see RaSH"I's commentary (on 'al - "along with" which), he explains as "next to". In my modest opinion, it ('al) can be explained as being literal: They brought the jewels "on the women", while they were wearing them, and Moses then had them removed. The reasoning is that it says "from every person whose heart so moves him". According to this, the men and women were led by their generous hearts, despite the need to adorn the women and their having no other (jewels). Also, to prevent you from saying that the men may have brought the women against their wishes, since women can be tightfisted, in particular with their adornments. To remove any such doubt, they were brought (the jewels) on the women.