288 " ROBERT T. HANCE 



I. INTRODUCTION 



While examining a number of paramoecia taken from a lab- 

 oratory culture in the early part of January, 1915, one individual 

 was seen to have three instead of the usual two contractile 

 vacuoles. Subsequent examination of the stock from the origi- 

 nal culture showed that a large percentage of the animals pos- 

 sessed the extra organs. Several animals with three vacuoles 

 were therefore isolated and pure lines started from them. It 

 soon became evident that the potentiahty for one supernumerary 

 vacuole was not only inherited but that the offspring might 

 possess even more than one extra contractile organ. A prelimi- 

 nary account of the behavior of these organs in heredity was 

 published some months ago (2). 



The discovery of such a marked variety of a form which has 

 served as a basis for so much valuable study opens an interest- 

 ing field for investigation. Parts of this report must necessarily 

 be of the most preliminary sort and various portions will be 

 completed from time to time and published separately. The 

 finding of the new race of paramoecium affords opportunity for 

 comparison with the common race and for a study of the physio- 

 logical activities of the two varieties. The following points will 

 be considered more or less completely in the following paper: 



1. The extra vacuole gives a definite character in the Protozoa 

 whose inheritance can be traced. The existence of two races 

 differing as far as is known only in this one character gives an 

 opportunity of crossing the two races by conjugation and of 

 determining whether inheritance in protozoa is Mepdelian as it 

 is in the metazoans. 



2. A comparison of the two races may be helpful in the 

 analysis of the function of the contractile vacuole. 



3. Some light may be thi'own on the process of conjugation 

 through a study of the behavior of both races. 



II. TECHNIQUE 



A separate pipette was used for each culture to guard against 

 cross contamination and was hung in a special holder attached 



