1913] 



Alfred P. Lothrop 



289 



process and that this has no primary relation to the activity of the 

 phagocytes. 



It is conceivable that if phagocytosis is the principal factor, the 

 blood-counts (differential and with the hemacytometer) would show 

 both an increase in the total number of leucocytes and a difference 

 between numbers of polymorphonuclear forms, in the bloods of a 

 larva in which the process of metamorphosis has not begun and of 

 a transforming individual. On account of the great difficulty in 

 identifying the various forms of leucocytes in hemacytometer 

 preparations, this method of counting was not adopted, but the 

 counts were made upon smears, stained with Wright's stain. Three 

 sets of individnals were used: (i) Larvse in which the appendages 

 had not appeared «and hence no absorption of the tail had begun; 

 (2) individuals in which the process of absorption had progressed 

 to some extent and (3) those in which the absorption had been com- 

 pleted for a number of months, i. e., adult frogs. Twenty-eight 

 specimens were used and the percentage results are as f ollows : 



The polymorphonuclear type runs slightly more numerous in 

 the individuals undergoing metamorphosis than in individuals before 

 the process has begun, but they are found in much larger quantities 

 in adults than in either of the other two groups. As Friedsohn and 

 Neumann have shown, however, it is impossible to distinguish young 

 polymorphonuclear leucocytes in the blood of amphibian larvse f rom 

 young erythrocytes and other forms of leucocytes, since all of the 

 corpuscles originate from cells similar in appearance in all cases. 

 Hence, the number of large nucleated forms doubtless includes 

 young polymorphonuclear leucocytes; and if this were so, it would 

 be expected that the number of the large ones would be smaller in 

 adults, which is the case as seen in the above column of values for 

 large mononuclear leucocytes. For these reasons, it is doubtful if 

 there is any decided difference in the number of polymorphonuclear 

 leucocytes in any stage of frog development; and therefore it is 



