Full Idea
A newly fertilized ovum, a newly implanted clump of cells, is no more a person than an acorn is an oak tree.
Gist of Idea
A newly fertilized ovum is no more a person than an acorn is an oak tree
Source
Judith (Jarvis) Thomson (A Defense of Abortion [1971], p.125)
Book Reference
'Ethics for Modern Life', ed/tr. Abelson,R./Friquegnon,M [St Martin's 1987], p.125
A Reaction
This relies heavily on the philosopher's concept of a 'person', but it seems right to me.