374 C. H. MARTIN. 
(1) It is interesting to notice that both Fraipont and 
Keppen examined individuals during a conjugation epidemic. 
During the conjugation epidemic which I had the oppor- 
tunity of observing I found, especially in material fixed 
during the commencement of the period, numerous examples 
of these long processes. ‘The early stages of their formation 
are analogous to those of the formation of the conjugating 
processes, as may be seen by a comparison of text-fig. 6 and 
Pl. VII, fig. 9. I was never able to see an instance in which 
one of these so-called buds became free, but in several 
examples from later material I have found evidence of 
change in the nucleus (PI. VII, fig. 9). 
Although I have not been able to follow out these stages 
in detail, the appearance of the macronucleus is absolutely 
identical with the fibrillar stage which occurs previous to the 
fragmentation in normal conjugation. 
I am inclined to believe that under certain circumstances, 
e.g. the absence of mature neighbours within range, a pro- 
cess of parthenogenesis occurs similar to that described by 
Hertwig for Paramecium aurelia (p. 224), and by means 
of which Prandtl later has explained the behaviour of the 
third individual in cases of triple conjugation in Didinium. 
It would seem that the chances against two neighbouring 
acinetaria exhibiting at the same time the three generally 
accepted symptoms of conjugation, viz. (1) sexual maturity, 
(2) distant relationship, (3) starvation, would be far more 
remote than the chance of meeting of two free swimming 
infusoria. And accordingly it is not surprising that in 
preparations made during a conjugation epidemic such 
appearances of presumable parthenogenesis are fairly fre- 
quent. 
(2) Conjugation between a fixed individual and a 
free ciliated bud. 
It is under this heading that I feel inclined to place 
Keppen’s figure (49). I beheve that this process is rare, 
