As a precursor to more complex forms of bisexual reproduction a number of simple plant and animal species learned to "con jugate", i.e. to exchange genetic material between the individuals within a species in such a way that the offspring could be distinct from either parent. The classic example among plants is Pandorina, a 16-cell species: the cells are loosely attached and each has a pair of flagella, of protoplasmic whips, for the purpose of locomotion through the water. To reproduce, the cells separate and fuse with the similar cells from another floating colony. The common bread mould represents another instance of primitive plant conjugation. The mould grows in the form of a mass of microscopic threads collectively known as a mycelium. Threads of two different kinds come together to form a special type of spore in which a blending of genetic material has taken place. It may be fanciful to call the two kinds of threads, respectively, male and female, but this is a clear instance of early bisexual reproduction.