Our knowledge of the genetics of protozoa is rudimentary, and it is time that the subject was studied. Walliker gives a good introduction to what is known about the genetics of some of the parasitic protozoa, which should serve as a base from which to carry out further investigations. He does not deal with all parasitic protozoa, but only with some of the malaria parasites, coccidia, and trypanosomes. These, he says, are the only ones in which such studies are well established. After a 2.5-page introduction and an 8-page chapter on definitions and technics, he discusses the genetics of malaria parasites (102 pages), coccidia (22 pages), and trypanosomes (32 pages). Even here he is selective. For instance, only Eimeria and Toxoplasma are discussed among the coccidia, and only Trypanosoma brucei and T. cruzi among the trypanosomes. So little is known about most of the others that it would hardly be worthwhile to include them.