METABOLISM 275 



said that pale stentors were often infected by a great number of 

 bacilli and that normal ones showed none. A pathological cause 

 seems unnecessary, however, because every time I isolated one of 

 these stentors the normal coloration was eventually regenerated. 

 Why an occasional stentor should pass through this depigmented 

 stage remains a mystery and problem. A suggestive parallel is 

 found in the chimera studies, in which a small graft oi polymorphus 

 causes the depigmentation of a coeruleus host. 



(b) OVER-PIGMENTED STENTORS 



Sometimes one finds stentors which are very dark in color, 

 appearing deep red by reflected Hght. Such animals may appear in 

 the same culture in which depigmented stentors are found and 

 have also been observed to be capable of oral reorganization and 

 to recover the normal pigmentation. Generally these ''reds" were 

 smaller and thinner than normal stentors, and lacking in food 

 vacuoles, but the nucleus appeared normal. The pigmentation of 

 the granular stripes is in these specimens supplemented by an 

 overload of pigment granules in the endoplasm. Though some 

 recover, others become exceedingly abnormal and are characterized 



b 



Fig, 76. Over-pigmented phase of S. coeruleus. 



A. Such specimens are smaller than the average (to the left) 

 probably by undernourishment because they show no food 



vacuoles, and the coloration is very dark blue-green. 



B. Later stage, showing disorganization, some extraordinarily 

 broad pigment stripes, and abundant pigment granules inside. 



Alternatively such animals may return to normal. 



