SI X IN PRoro/oA 151 



rions of such tusiii<4 iiulix idiials showed nuclear conditions somewhat 

 like those reported l)\- Dohell (1908) for Copromonas siibtilis (H to 

 15). I lowcver. Bunting did not claim that a process of syngamy had 

 taken place. These processes of cell fusion probably are significant, 

 and further studies arc needed with that possibility in mind. 



The onh' satisfactory accounts of syngamy in members of the 

 Polymastigina are those of (Cleveland for the flae^ellates living in the 

 gut of the wood-eating roach, Cry ptocerciis pmictiilatus. The same 

 may be said for the Hypermastigina. A review of Cleveland's papers 

 follows. 



HORiMONE-INDUCED SEXUALITY IN ANIMAL FLAGELLATES 



One of the most interesting developments in the field of sexual 

 reproduction in Protozoa is the occurrence of syngamy in the flagel- 

 lates that inhabit the gut of the wood-eating roach. Cry ptocerciis 

 pinictulatus. These conditions have been brought to our attention by 

 Cleveland who, with his associates, published an extensive paper on 

 the morphology, taxonomy and host-parasite relations of this group 

 of flagellates in 1934. 



More recently Cleveland has begun a series of papers revealing 

 the details of "sex" in these flagellates. In two preliminary papers 

 (1947a,b) this author noted that the flagellate fauna of the roach 

 consists of some twenty-five species distributed into two orders, eight 

 families, and twelve genera, ranging from relatively simple polymas- 

 tigotes to extremely complex hypermastigotes, all of which exhibit 

 some form of sexual behavior at the molting period of the host. Be- 

 tween molts, no sexuality occurs. In termites, closely related flagel- 

 lates do not exhibit any sexual activity. At each molt of termites, the 

 flagellates are lost and must be regained from other members of the 

 termite colony by proctodaeal feeding. 



Cleveland believes that the sexual activities of the flagellates in 

 Cry ptocerciis are induced by some direct effect of the molting hor- 

 mone of the host, rather than by an indirect effect through such 

 agencies as a decrease in food supply, increase in carbon dioxide, or 

 decrease in oxygen, all of which occur during molting. 



One remarkable feature of this behavior is that different flagel- 

 lates follow different patterns of sexual activity, both in relation to 

 the process of molting itself and in relation to the various ways in 



