156 PROTOZOOLOGY 



were called the mating types. Soon a similar phenomenon has been 

 reported by several workers in five other species of the genus ; namely, 

 P. hursaria, P. caudatum, P. trichium, P. calkinsi, and P. multimi- 

 cronucleatum. When organisms which belong to different mating 

 types are brought together, they adhere to one another in large 

 clumps ("agglutination") of numerous individuals (Fig. 78, h). 





--7; J'' l- 

 1 - ■> ' J - ' ' 





-%». *^-. 



V V *- 



« 



o ' r 





• 4 





'> ;% ♦ v« • 







Fig. 78. Mating behavior of Paramecium hursaria (Jennings), a, indi- 

 viduals of a single mating type; b, 6 minutes after individuals of two mat- 

 ing types have been mixed; c, after about 5 hours, the large masses have 

 been broken down into small masses; d, after 24 hours, paired conjugants. 



After a few to several hours, the large masses break down into small 

 masses (Fig. 78, c) and still later, conjugants appear in pairs (Fig. 

 78, d). The only other ciliate in which mating types are definitely 

 known to occur is Euplotes patella in which, according to Kimball 

 (1939), there occurs no agglutination mating reaction. 



How widely mating types occur is not known at present. But as 



