PAPERS ON ZOOLOGY AND PHYSIOLOGY 321 
4. Correlation tables between parents and immediate pro- 
geny in regard to any variable characters are deceptive in 
showing the results of selection in inheritance work. They 
should only be used in connection with graphic pedigree charts, 
and complete notes on environmental factors. When cor- 
relation tables were so used in regard to my selection work in 
Aphis avenae they substantiated in almost every case, the in- 
terpretations previously made. 
5. The recent work which has been done in pure lines giv- 
ing positive results in regard to selection, is to a certain extent 
open to the criticisms of the earlier work in pure lines which 
gave chiefly negative results. 
6. It is very probable, as Jennings has pointed out, that 
the mechanism of inheritance in certain lower organisms is 
quite different from that of higher animals which have a uni- 
parental type of reproduction. This difference may be so 
great that the principles of the pure line theory will not apply 
to them, in most respects at least. 
7. Recent investigations in pure lines seem to have given 
us the much desired rigid tests called for by earlier critics, 
and these results are not in accord. 
8. The pure line theory will probably not apply to such 
large classes of organisms as was at one time supposed, and 
may be modified in some respects in regard to those classes to 
which it does apply. 
9. In higher organisms with a uniparental type of repro- 
duction we have no strong evidence against the application of 
the main principles of the pure line theory of inheritance. 
LITERATURE 
Ackert, J. E., 1916. On the Effect of Selection in Parmaecium. Genetics, Vol. 
I, pp. 387-405. 
Barber, M. A., 1907. On Heredity in Certain Micro-organisms, Kan. Univ. Sci. 
Bul., Vol. IV , No. 1, 48 pp. 
East, E. M. 1910. The Transmission of Variations in the Potato in Asexual Re- 
production. Conn. Exp. Sta. Rept., pp. 119-160. 
Ewing, H. E., 1914, a. Pure Line Inheritance and Parthenogenesis. Biol. Bul. 
Vol. XXVI, pp. 25- rr 1914 b., Notes on Regression in a Pure Line of Plant Lice. 
Biol. Bul. Vol. } XXVII, pp. 164-168. 1916, Eighty-seven Generations in a Partheno- 
genetic Pure Line of Aphis Avenae Fab. Biol. Bul., Vol. XXXI, pp. 53-112. 
Jennings, H. S., 1908. Heredity, Variation and Evolution in Protozoa II. Proc. 
Amer. Phil. Soc., Vol. XLVII, pp. 393-545. 1909, Heredity and Variation in the 
Simplest Organisms. Amer. Nat. Vol. XLIII, pp. 321-337. 1911, Pure Lines in the 
