PROTOZOAN FAUNA OF HAY INFUSIONS 251 
The close agreement both of the sequence of appearance and of 
maximum numbers in all three series (A, B, C) is striking (cf. p. 
244) and indicates that the sequence is not merely the result of 
factors incidental to the methods employed. 
The data in regard to the time of disappearance is relatively 
meagre for the A and C series because many of the typical forms 
studied survived the period of the last observation. Consequently 
the sequence of time of disappearance is based chiefly on data from 
the B series, which, on account of the removal of the hay, passed 
through its cycle much more rapidly. 
It is remarkably suggestive that the sequence (derived from the 
entire series of infusions) of all the forms at the time of appearance 
and at the time of maximum numbers and at the time of disap- 
pearance is zdentical, with the exception of Amoeba. The data 
indicate that the Amoeba cycle in the infusions is comparatively 
short since the position of Amoeba in the series advances progres- 
sively forward: it being last at the time of appearance, next to last 
(before Vorticella) at the time of maximum and third from last 
(before Paramaecium and Vorticella) at the time of disappear- 
ance. However, as has been already pointed out, the data is not 
sufficient to positively establish the relative position of Amoeba 
and Vorticella at the period of maximum numbers. 
A study of the curves plotted from the surface counts of single 
infusions or groups of infusions reveals the fact that when once 
a great development is attained by a particular form, this maxi- 
mum is seldom approached again. There are, however, some 
striking exceptions to this as, for example, Colpoda in group A III 
(cf. fig. 3) and the Hypotrichida in group C IV (ef. fig. 11). 
The curves further show that the major rise and fall in numbers 
are usually of about equal rapidity, though the final complete 
disappearance of an organism from the infusion may be long 
deferred. Careful searching in many of the A and B infusions 
sequence of forms with the one here described. Among the monads, however, he 
found a large development of Chilomonas, while this form was. relatively scarce 
in my infusions. Also, his Amoeba fauna was partially replaced by a consider- 
able growth of Arcella. This latter result is interesting since it shows that some- 
what closely related rhizopods fill substantially the same place in the economy of 
the infusions. 
