82 Regulation of Size in Unicellular Organisms 



cium caudatum (DeGaris, '27). These monsters re- 

 produced individuals of normal size, but the forma- 

 tions persisted for several generations. Similar for- 

 mations were induced by ultraviolet radiations, accord- 

 ing to Hinrichs ('28) and MacDougall ('29). The pos- 

 sibilities of all these methods of inhibiting reproduc- 

 tion appear to be great enough to warrant their ex- 

 tensive use in investigating the nature of cytoplasmic 

 size regulations. 



Numerous observations of the inhibition of fission, 

 in media containing chemical substances, have been 

 made upon bacteria. In the presence of urea or of 

 human urine, Bacillus coli formed filaments up to 120 

 micra in length (Wilson, '06). Salts such as calcium 

 chloride and magnesium chloride stimulated the for- 

 mation of large individuals in various species (Hata, 

 '08). Similar influences were exerted by modified hy- 

 drogen ion concentrations (Reed and Orr, '23). Vari- 

 ous dyes were effective in producing the formation of 

 long filaments; the experiments of Vay ('10) seem 

 to indicate that the effects were highly specific. Revis 

 ('12) described the appearance of long, branching fila- 

 ments of Bacillus coli when grown on agar media con- 

 taining malachite green. These filaments were said to 

 contain no cell walls, as though formed by the growth 

 of bacilli which did not multiply. 



These are a few cases out of a number which have 

 been described for various bacteria. Apparently in 

 none did the observers follow out what might be im- 

 plied in "Koch's laws", obtaining back normal individ- 

 uals by subsequent culture. But in numerous instan- 

 ces where monstrous "involution forms" of various 

 species of bacteria have been obtained, the more famil- 

 iar forms appeared again after return to normal fission 

 rates upon new and adequate medium (Lohnis, '21; 

 Henrici, '28). 



