Bjorn A. Afzelius,1 who for many years has been interested in cilia of one sort or another, describes in a recent issue of Science a bizarre, inborn disorder in four men who, while seeming to possess respectable sperms, have nothing with which to propel them. The sperm are immobile. This sad plight, it turns out, is caused by missing dynein arms, which are "structures that in normal cilia, flagella, and sperm tails form temporary cross bridges between adjacent filaments... for generating a beating movement of cilia or sperm tails."
Afzelius entertained the idea that these spermatozoa could not synthesize normal dynein arms. Three of his subjects had situs inversus. Perhaps the normal circular beat of the embryogenetic cilia had turned appositely around and so prevents any beat at all. Newman2 had reported that when the unhatched blastulas of starfish larvae were chilled, the number of larvae with situs