276 M. M. Mercaur 
body, it not occuring until the daughter nuclei are separated to a 
considerable distance, so that the division of the body (transverse 
in this case) could easily pass between the daughter nuclei, produ- 
cing thus in each daughter cell a truly binucleated condition. 
It seems to me quite probable that such has been the history 
of the evolution of the binucleated condition in higher Cilzata: first 
delay in division of the body, establishing a temporary binucleated 
condition; then complete suppression of this delayed division of the 
cell-body, establishing a true binucleated condition, each nucleus, as 
apparently now in Paramaecium, belonging to a potentially, but not 
actually, independent individual. 
The remarkable phenomena which NeEresHEemmeER (1908) descri- 
bes for Ichthyophthirius probably cannot be brought into harmony 
with the interpretation of the nuclear conditions in the Ciliata here 
suggested. There are gaps in NERESHEIMER’S work, and an absence 
of detail in both figures and description, which make it desirable 
that this genus be further studied. 
Compound nature of the Ciliata. 
The truly binucleated forms, as well as the falsely binucleated 
Opalinae are really potentially double individuals; and similarly the 
multinucleated Opalinae, arising by further temporary suppression of 
divisions of the body, are highly compound forms composed of many 
potential individuals. These individuals all become ultimately distinct 
before or in connection with copulation, even in the multinucleated 
Opalinae, the temporarily suppressed divisions of the body finally 
appearing rapidly in the spring and producing unicellular gametes.’) 
The phenomena in the spring which preceede and 
accompany copulation. 
Phenomena in Opalina intestinalis. 
As the breeding season of the host approaches most of the 
Opalinae in the rectum increase the rapidity of their division, be- 
1) The fact that the macrogametes are often still binucleated at the time of 
conjugation does not indicate that they are really binucleated forms, but merely 
that conjugation may occur before the complete separation of the definitive gametes, 
as if fertilization in a Metazoan should occur before completion of the maturation 
of the egg. Compare pages 285 and 290. 
