358 C. H. MARTIN. 
fig. 50 shows the macronuclei drawn out into long strands 
and two micronuclear spindles, and fig. 31 shows an Acineta 
with a new light-staining nucleus surrounded by the small 
spherical products of the degeneration of the old nucleus. 
At the time at which Keppen wrote the part played by the 
micronucleus in the conjugation of ciliates was not thoroughly 
understood, but it is to him we owe the first definite recogni- 
tion of a micronuclear spindle in an acinetarian. 
At the date at which Biitschli wrote his account of the 
Suctoria in ‘Bronn’s Thierreich’ there were numerous iso- 
lated references to conjugation amongst Acinetaria to be 
found in the literature of this group. But as the only 
observers—Plate and Schneider—(with the exception of 
Keppen vide supra) who had followed the internal changes 
connected with this process, denied the existence of a micro- 
nucleus, it will be seen that much remained to be done. 
Biitschli himself remarks, p. 1917:—‘‘ Die vorstehenden 
Erwagungen zeigten, dass Copulationen nicht mit geniigen- 
den Sicherheit erwiesen sind. Dagegen ist fiir die Dendroco- 
metinen sicher, dass ihre conjugation im Wesentlichen wie 
die partielle der Ciliaten verlauft, woraus wohl geschlossen 
werden darf, dies gelten auch fur die tibrigen, nicht genauer 
untersuchten Conjugation.” 
In Maupas’ paper, ‘‘Le Rajeunissement Karyogamique 
chez les Cilies” (1889), he mentions without figures the 
results he had obtained in the conjugation of two acine- 
tarians Podophrya fixa and Podophrya cyclopum. In 
both these forms there is only a single micronucleus, and in 
Podophrya cyclopum there is apparently complete fusion 
without the previous existence of any differentiation between 
the two gametes. 
Maupas describes the conjugation of Podophrya fixa, 
which, as in the case I describe, is partial, in the following 
words (p. 385) :—“ Chez la Podophrya fixa j’ai observé les 
stades A, B, C and H Pendant ce dernier stade je n’ai jamais 
vu qwun seul nouveau corps nucléaire et un seul micro- 
nucleus. Je ne serais donc pas étonné que la seconde 
