396 SUMMARY OF CURRENT RESEARCHES RELATING TO 



majority of cases increases the length of life of the exconjugant line' 

 In 80 p.c. of cases the total number of generations attained by the 

 exconjugant exceeds those attained by the parent from the date when 

 the exconjugant arose to the death of the parent. The fact is evident 

 that conjugation increases the number of fissions to a total which could 

 not otherwise have been reached. Over 80 p.c. of the exconjugant lines 

 attained more generations than their respective parent lines. By con- 

 jugation it has been possible to increase the number of fissions to more 

 than double that obtainable without conjugation. In short, the survival 

 value of conjugation is marked in the majority of cases — the exconju- 

 gant lines exhibiting a higher division rate than the non-conjugant 

 Hnes and outliving them. J. A. T. 



Effect of Conjugation on Division Rate. — L. L. Woodruff and 

 Hope Spencer {Froc. Soc. Exp. Biol, and .Medicine, 1921, 18, 240-1). 

 Experiments with Spathidium spathida lead to the conclusion that the 

 exconjugant lines of a pedigree culture exhibit, in the great majority of 

 -cases, a higher division rate for the first fifteen days after conjugation 

 than the parent lines. Exconjugation lines which are derived from old 

 parent lines (i.e. from lines which have undergone many generations 

 since conjugation) show a relatively greater increase in the division 

 rate, during the first fifteen days, as compared with the parent lines, 

 than do exconjugant lines which are derived from young parent lines 

 (i.e. from lines which have more recently conjugated). J. A. T. 



Amicronucleate Race of Didinium nasutum. — Mary W. Patten 

 {Proc. Soc. Exp. Biol. Medicine, 1921, 18, 188-9). From a micronucleate 

 parent race a single amicronucleate exconjugant appeared, and the 

 condition persisted for 652 generations. At various intervals during 

 the life-history of this culture there were periods showing a tendency 

 for encystment and conjugation, but the animals which encysted or 

 conjugated invariably died, a fact undoubtedly related to their amicro- 

 nucleate condition. There was no endomixis. The amicronucleate 

 state doubtless arose from some irregularity in conjugation. J. A. T. 



Measurements of Trypanosoma diemyctyli. — R. W. Hegnee 

 [Journ. Farasitologij, 1921, 7, 105-13). Every one of seventy-eight 

 aquatic specimens of the newt Diemyctylus viridescens was found to be 

 infected with Trypanosoma diemyctyli Tobey. Measurements were made 

 of trypanosomes from ten newts, which showed differences in their 

 range of variation in total length exclusive of the flagellum, in the 

 length of portions, and in the width of the body, and in the averages of 

 length and width. Length and width show a positive correlation, and 

 on an average the longer the specimen the wider it is. Two different 

 types occur in one and the same host. Two different types obtained 

 from the different newts are probably races of one species that are 

 heritably diverse in size. They may, however, belong to different species, 

 or may be sexual phases of a single species, or may differ because 

 of chano;es due to the environment. J. A. T. 



^&^ 



New Flagellate with Trichocysts. — W. Conrad {Bidl. Acad. Roy. 

 Belgique Classe des Sciences, 1920, No. 11, 541-55, 4 figs.). A de- 



