86 S^-MBIONTICISM AND THE ORIGIN OF SPECIES 



other variety is a form of coccus. He was able to cultivate 

 them in an agar-peptone medium in which they were col- 

 lectively colored light yellow and were opalescent. 



The bacteria that developed in Pierantoni's culture ex- 

 periments did not exhibit luminescence in the culture 

 media. Buchner remarks in this connection that the 

 sceptic finds, in this circumstance, grounds for interpreting 

 the cultured bacteria as contaminations. He also points 

 out that a doubter might be inclined to call these bacteria 

 "plastids," "vacuoloids," or "mitochondria." However, 

 Buchner refers to a similar condition of affairs in connec- 

 tion with his own experiments on some parasitic luminous 

 bacteria in the wood louse. When these bacteria were 

 cultivated in artificial culture media they did not exhibit 

 luminosity. When the cultured organisms were inoculated 

 into a wood-louse the luminosity returned. Buchner 

 beUeves that the symbiotic bacteria cultivated by Pieran- 

 toni might have responded in Uke manner. 



The cells containing urate crystals do not belong essen- 

 tially to the Imniniferous organ. They are absent in this 

 organ in some species, and are present in the fatty tissues 

 of some insects which are not luminous. It was mentioned 

 above that symbiotic bacteria may be associated with these 

 cells. 



There is considerable variation in the tracheal supply to 

 the luminiferous organs in different species. M. Schultze 

 described the morphology of the trachea in the Lampy- 

 ridae. He found the finer tracheal tubules extending into 

 the cells. It has been shown by various authors that 

 oxygen is utiUzed in the Hght-producing process in these 

 forms. The experiments of MoUsch in this field are con- 

 clusive. When air is denied to Ught-producing bacteria 

 there is no luminosity, but when a bubble of air is brought 

 in contact with the bacteria they again emit hght. Bei- 

 jerinck ('89) mixed a bouillon culture of luminiferous 



