80 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



the bacteriocytes in young animals also contain glycogen. 

 In older animals he found only fat and uric acid concre- 

 tions. 



Mercier investigated the bacteriocytes after starvation, 

 and found morphologic variations in the bacteria, apparently 

 due to inanition. In an animal that was infected with 

 a yeast-Hke parasite, the bacteriocytes were not present. 



Blochmann, Mercier, Buchner, and Frankel have shown 

 that the bacteria are transmitted from one generation to 

 another in the egg cell. Heymons ('95) studied the bac- 

 terial symbionts in embryonic development, and demon- 

 strated their presence in all stages. 



Symbionts in ants were first observed by Blochmann 

 ('84-'87); In the midgut of Camponotus ligniperda, pecu- 

 liar cells filled with bacteria-like rods are constantly pres- 

 ent. So also in Formica fusca there are two cell-groups of 

 similar appearance near the ovaries. He also observed the 

 bacteria-like rods in the ova. Strindberg ('13) believed the 

 rod-shaped structures to be mitochondria. Buchner in- 

 vestigated these bodies and concluded that they were fungi. 

 The cells in which they are present he calls "mycetocytes." 

 The development of the ova and the infection of the egg 

 have been clearly described by Buchner. After the ova 

 have entered the oviduct and the nurse cells have come into 

 position, the symbiotic rod-shaped fungi begin to enter the 

 follicle cells. A httle later they penetrate the ova as well 

 as the nurse cells. When the ovum has increased to about 

 three times its original size, the follicle cells contain but 

 few symbionts, but the ovum is so packed with them that 

 the cytoplasm of the egg cell is obscured. The host-cell 

 plasm now increases in amount, and at the same time 

 appears to have assumed a control over the growth of the 

 symbionts, for they increase no further. Buchner believes 

 that this is a chemical regulation. A httle later the yolk 

 begins to accumulate in the egg cell. During this process 



