SFX IN PROTOZOA I43 



more, plus and minus clones could be established. Filtrates from plus 

 clones induced gamete formation in minus clones and vice versa. 

 Ciamctes from any one clone did not fuse with each other. When 

 mixtures of plus and minus clones were made, gametes from any 

 plus clone would unite with those of any minus clone and vice versa 

 (Table I). This demonstration of the formation of chemical attrac- 

 tants is a matter of great interest; it recalls the claims of iMoewus and 

 others for chemical attractants in Chlmuydovionas (see paper by 

 Lewin). 



Duboscq and Collin (1910) described phenomena interpreted 

 as sexual reproduction in parasitic dinoflagellates living in some marine 

 tintinnoid ciliates. In his monograph on parasitic dinoflagellates, Chat- 

 ton (1920) called this parasite Duboscquella tintinnicola and stated 

 that "gametocytes" were produced from larger, vegetative stages by 

 successive divisions. Two divisions, probably meiotic, then produced 

 flagellated gametes which had something of the appearance of Oxyrrhis 

 viariiia. These fused in pairs, producing zygotes which rounded up 

 and lost their flagella. Further development was not followed. Later, 

 Chatton (1927) described meiotic gametogenesis in Paradiniimi 

 poiicheti, a parasite of the body cavity of larger copepods of the 

 genus Acostta. The flagellispores which developed were considered 

 to be haploid gametes, but fertilization was not observed. Chatton 

 and Biecheler (1936) described fusion of flagellispores (Fig. C, 9 

 to 12) formed by the parasitic dinoflagellate Coccidimum mesnili 

 which parasitizes another dinoflagellate, Crypotperidijmim. Thus 

 there seems to be very strong evidence for syngamy in this group. 



Order RhizoiJiastigina 



Kudo recognizes four orders in the Zoomastigina: Rhizomas- 

 tigina, Protomonadina, Polymastigina, and Hypermastigina. 



In the Rhizomastigina we have the accounts of sexual reproduc- 

 tion in Mastigella vitrea and Mastigina setosa by Goldschmidt (1907). 

 "Chromidia" were said to give rise to "secondary nuclei," each of 

 which with a bit of cytoplasm became a "gamete." The gametes were 

 said to emerge from parents and fuse to form zygotes which grew into 

 adults. Belaf (1926) stated that these accounts were based on misin- 

 terpretations involving small fungoid parasites. However, Ivanic 

 (1936) has described "copulation" in Mastigina hylae, an amoebo- 



