MORE COMPLICATED LIFE CYCLES 



117 



formed was named by Hertwig, in 1902, "chromidien," from which 

 the term chromidia is derived, a term now universally employed by 

 protozoologists. According to Hertwig this latter material in actino- 

 spherium cytoplasm is prophetic of the death of the animal, for when 

 it is thus formed the renovation of the cell is impossible (1904). 



Fir,. 44 



Arcella vulgaris. 



(After Calkins.) Three individuals in pla.-tngamic union. 

 P, idiochroinidia; X, nuclei. 



FIG. 45 



A^? * !<s 



l^-/&> ^fy^ 







r; "> 



> 



Chromidia formation in Actinospherium eichhornii. (After Hertwig.) A, primary nuclei 

 and chromidia; B, complete transformation into chromidia. 



It thus appears that we have to do with two kinds of chromatin 

 masses in the cell body and no little confusion has arisen in conse- 

 quence of the mixed terminology applied to this material, which is alike 

 in origin from the nucleus but very different in function. Chromidia, 

 in Hertwig's sense, is functionless extranuclear chromatin, but Schau- 

 dinn and others have used the term to designate the sexual chromatin 

 which is equivalent to the chromidialnetz in Hertwig's terminology. 



