MITOCHONDRIA IN PROTOZOA 125 



This conclusion was reinforced recently by the discovery of a 

 vital dye known as Janus red, which is the sodium salt of diethyl- 

 safranine monocarboxylic acid. This dye, found by Brailsford 

 Robertson, has been employed by Horning (61), and found to stain 

 mitochondria selectively, leaving bacteria unstained. The variety 

 of bacteria tested does not leave much doubt as to its 

 specificity. Although Janus green B was fairly selective, it also 

 stained other cell organs, such as the Golgi apparatus, in certain 

 cases {Helix spermatids), and also some forms of bacteria. 



Using this and other methods of demonstrating mitochondria, 

 Horning has investigated their distribution, form and function 

 in the protozoa and some metazoan cells (pancreatic cells). 



As regards their distribution, they appear to have a distinct 

 tendency to adhere or remain near to protoplasmic surfaces. 

 Thus they are found in dense aggregates on and about the surface 

 of the nucleus (63). He was unable to trace any penetration of 

 the nuclear membrane, as Rikita Honda had claimed. In all 

 probability the latter's claim is based on badly-fixed material. 

 He debates the possibility of their adherence to the surfaces being 

 a surface tension phenomenon. The final suggestion is that it is 

 explainable on the grounds of their phosphatidal nature. Phospha- 

 tides, like other fatty substances, tend to collect at interphase 

 surfaces, since they reduce surface tension. 



This explanation is also used to account for their position in 

 other parts of the cell. In Opalina and Paramoecium they may be 

 found arranged in rows just below the cuticle, between the bases of 

 the cilia (64), Their disposition is different in the two cases. In 

 Opalina they are arranged as rods, the long axes of which lie at 

 right angles to the longitudinal rows of cilia, parallel to the 

 surface of the cell. In Paramoecium the mitochondria lie end to 

 end in rows, so that the long axes of the rods lie parallel to the row 

 of cilia. It is suggested by Horning that as the general distribu- 

 tion is similar, the differences may be explained on the grounds 

 that in Opalina the rows of cilia are wide apart, and thus allow 

 the mitochondria to lie across between the ciliated lines, but in 

 Paramoecium the cilia are close together, so that the mitochondria 

 must lie lengthwise. Although only two cases are thus quoted to 



