SOME OBSERVATIONS ON ACINETARIA. 373 
chromatin granules, and all traces of the old macronucleus 
have disappeared (Pl. VII, fig. 8). 
External budding.—It will be now necessary to refer to 
a process which Keppen has termed ‘“ external budding,” 
and which he describes as the development of a lateral out- 
growth, which may be followed by disappearance of the 
tentacles. He found that this outgrowth may change its 
shape and size considerably, and after a period of ten to 
twelve hours the animal may return to its original shape. In 
some very rare cases the outgrowth may break off, but he 
was never able to determine the fate of the bud so formed. 
In several cases he observed the nucleus carried to the 
boundary between the acinetarian and the so-called bud, and 
under these conditions he found appearances of fragmenta- 
tion of the nucleus, though there was nothing to suggest a 
normal division. 
In one case (fig. 47) he found a specimen of Acineta 
papillifera with a spade-like body containing a nucleus, 
and covered with moving cilia attached near the tentacles. 
This body, owing to its resemblance in shape, he was inclined 
to compare to the outgrowths described above. The body 
remained in contact with the acinetarian for some time, until 
they were finally both lost. 
These structures are probably identical with those which 
Fraipont had previously described as “ diverticules généra- 
teurs”’ in acinetan division, and which, according to him, 
were not to be regarded as external buds, but as structures 
out of which endogenous ciliated buds were to be developed. 
This theory was based on a single observation in which he 
found a ciliated bud in contact with a fixed form. 
I believe that Keppen has confounded under this term two 
quite distinct phenomena— 
(1) The formation of long conjugation processes in indi- 
viduals which by reason of their position cannot come into 
contact with another individual ripe for conjugation. 
(2) Cases of conjugation between a fixed form and a free- 
swimming ciliated embryo. 
