204 SEX IN MICROORGANISMS 



There was also evidence that a single parasite, passed along from 

 parent to daughter during fission of the parent, was unable to carry 

 on the life cycle; that is, any individual parasite is male or female, but 

 not both. However, if a single spore containing two sporozoites can 

 give rise to both sexes, then the two sporozoites should be of different 

 sex. Otherwise a male spore and a female spore would have to be 

 taken into a new host to produce male and female gametes. 



In the case of Chagasella sp., Gibbs (1944) showed that after the 

 first division of the zygote nucleus in the oocyst (Fig. V, 19, 20) 

 only one of the two daughter nuclei divided (21). This differential 

 division, by analogy with Adelina deronis, could indicate maleness for 

 the nucleus that divided and femaleness for the one that did not. Thus 

 sex determination would be accomplished at the first nuclear division 

 in the zygote. During further development the cytoplasm of the 

 oocyst divided into three parts while the nuclei also divided, produc- 

 ing three sporoblasts which became spores (22-23). Each spore 

 produced four sporozoites (24-26). According to the suggested 

 interpretation, two of the spores would be male and one female. 

 However, Gibbs stated that the oocyst membrane gradually disap- 

 peared so that the saHvary glands of the host (a hemipteran insect) 

 often contained many single spores. This suggests that the spore is 

 the infective stage. 



The so-called spore of a gregarine, derived as it is directly from 

 a zygote, is equivalent to the oocyst of the Coccidia. It is interesting 

 that in gregarines generally, and in many of the Coccidia, the oocyst 

 is the infective stage. This should contain both sexes. When spores 

 develop in the oocyst, as in so many Coccidia, they might well be 

 male or female, but not both. Becker (1934) was able to maintain 

 infections of Eivieria in rats by inoculating a new host with a single 

 oocyst. Experiments are needed to see if a single spore of Emieria 

 (there are four in each oocyst) would be capable of maintaining the 

 life cycle if transferred alone to a new host. Why should the spore 

 not be an infective stage? 



Perhaps nature offers such an experiment in the case of Aggre- 

 gata eberthi, a coccidian that requires two hosts to complete the life 

 cycle (Fig. V, 1 to 18). According to Dobell (1925) this species 

 undergoes gametogony, fertilization, and sporogony in the cuttlefish. 

 Sepia officinalis, while schizogony takes place in the crab, Portunus 

 depurator. The zygote (1), formed in the cuttle fish, does not pro- 



