Studies on the Life History of Protozoa. 441 



period" in the inanition phenomena: "All gastric vacuoles and 

 food balls disappear during the first period. After this the small 

 endoplasmic granules are used. As a result of this the quantity 

 of endoplasm becomes much reduced. Toward the end of this 

 time the living substance of the endoplasm itself is used, in part 

 at least, to supply fuel for the continuing metabolism. Owing 

 to the disappearance of the inclusions of the endoplasm and to the 

 use of endoplasmic substance itself, the body form becomes more 

 or less distorted or changed. But even in those individuals in 

 which this has taken place and in which the form is considerably 

 changed, the ectoplasm with its trichocysts, the contractile vacuole 

 and the cilia are not altered in any noticeable manner. This 

 shows, therefore, that in the first period of inanition the first 

 materials to be used are the reserve stuffs which are normally 

 utilized for the ordinary fuel (life processes). Only when all of 

 the reserve material is used and when the endoplasm itself is first 

 attacked, and only when all food whatsoever is gone, will other 

 parts of the protoplasmic structures be attacked. When this time 

 comes the second period is inaugurated." (Loc. cit., p. 87.) 



In the second period of inanition there are more fundamental 

 changes, and the remainder of the protoplasmic structures are 

 involved. Ultimately the nucleus is affected and when this goes 

 the organisms are doomed. Wallengren's conclusions as to this 

 period are as follows: "The endoplasm, which at the beginning of 

 this last period was already considerably reduced, now appears 

 strongly vacuolized. The shining vacuoles which are probably 

 filled with the products of degeneration of the endoplasmic con- 

 tents, may attain to a considerable size. Along with this vacuol- 

 ization the ectoplasm becomes more and more absorbed and as a 

 result of this, the trichocysts are drawn into the endoplasm 

 streams and are probably digested. Along wnth them the small 

 papilliform swellings on the outer surface disappear, and with 

 these the small granules which in the living animal stain with 

 neutral red. The contractile vacuoles and their feeding canals 

 become reduced in the same proportion as the thinning of the 

 ectoplasm. A number of cilia are probably absorbed as a result 

 of the decreasing size of the whole animal, and the remainder of 



