154 WITHROW MORSE. 



instance is that whatever the process means, it is precursory to 

 phagocytosis. 



In the second figure, the same mobilization of the lipoids is to 

 be seen in the layer immediately proximal to the epidermis. 

 This does not appear in control organisms where the size of the 

 individual together with the character of the cellular elements in 

 the muscles and elsewhere negate the advent of metamorphosis. 

 Accompanying the so-called but misinterpreted " chroma tolysis" 

 is a vacuolization of the tissues, an edema recognizable in the 

 translucence of the tail when viewed in the individual intact and 

 alive. This edema formation is to be seen in the second figure 

 lying directly distally to the dark area. The vacuoles seen in the 

 epidermis, however, are normal skin glands. Regarding, now, 

 the question as to whether phagocytosis is a factor here, it must 

 be admitted that there is nothing to indicate the presence of these 

 agents. It is difficult to present this testimony in a black-and- 

 white photomicrograph, but sufficient detail is given to insure that 

 at least the process is not pari passu with the extent of edema 

 formation and of lipoid mobilization. Perusal of the micro- 

 scopic sections themselves makes it evident that no phagocytosis 

 is operative in these tissues, although there have been some 

 changes indicative of metamorphosis. 



From histological evidence, then, we must accept the belief of 

 Looss and others supporting him that phagocytosis as a primary 

 event is not a fact, but that its participation in metamorphosis is 

 a later and secondary event. 



In passing, it is of interest to compare the histological pictures 

 given by preparations of Zenker's or hyaline degeneration and 

 those given by the normal atrophy of the larval frog's tail. The 

 writer was first struck with this coincidence in examining the 

 photomicrographs of Steiner's (12) article on dermatomyositis. 

 From histological evidence and from physiological considerations 

 it is probable that the natural atrophy of the metamorphosing 

 tadpole is reflected in the pathological atrophy in cases of pro- 

 gressive muscle atrophy. 



From the evidence thus far submitted it is probable: 



i. That an event precursory to the appearance of phagocytes in 

 the affected areas occurs. 



