"The Return of the Blob"
At Magneto's strong-hold, the Brotherhood of Evil Mutants bicker. Professor X reveals his new invention, Cerebro, to Scott. It is a machine that locates mutants, much like the Professor's natural power allows. The Professor also names Cyclops as team leader, as he announces that he will be absent for some time. Magneto tracks down the Blob at the circus, cures his amnesia and recruits him for the Brotherhood. Cerebro alerts the X-Men, and soon, the two groups face off. Magneto is callous in regards to the Blob's safety, and the Blob decides he wants nothing to do with either group. 22 pages (X-768).
First appearance of Cerebro.
Reprinted in Marvel Super-Heroes (Vol 2) #26 (partial), and X-Men: The Early Years #7.