Tue Microscope. 57 
that of Podophrya fixa from which it differed in shape and orna- 
mentation. 
Doubtless, all who have even casually examined infusorial 
life have observed that certain zooids of the stalked species, 
when not suited with surrounding conditions, retracted their 
peristomal region and developed a posterior circlet of cilia, that 
after a longer or shorter time they loosed from their anchorage 
and swam away to establish themselves in more congenial quar- 
ters and grow a new pedicle and, if a compound variety, a new 
colony. In some species of the genus Zoothamnium the migra- 
ting zooids which are to found new colonies become abnormal 
and often greatly enlarged. I have occasionally met with the 
abnormal zooids of Z. arbuscula and the accompanying figure 
3 represents such before it has developed the posterior cilia or 
even withdrawn the anterior cilia. It will be seen that the nu- 
cleus is greatly enlarged, more coarsely granular and coiled, 
the cuticular surface coarsely aud transversely striate. I esti- 
mate that the bulk of the spherical one is forty times greater 
than that of the normal form. 
The act of binary division is frequently seen by those ob- 
serving Infusoria, but that of internal budding or the internal 
production of ciliate embryos is less frequently witnessed. In 
the Tentaculifera it is not rare, if one recognizes the fact when 
presented. One day in July last a gathering of pond weeds 
and small aquatic animals was brought in on which Podophrya 
quadripartita was abundant, and the form most numerous was 
the elongated variety. Among these many were found with 
embryos occupying the upper part of the body cavity. This af- 
forded an opportunity to observe the manner of escape of the 
embryos and to endeavor to witness the remarkable change in 
the nucleus attested by Biitschi, viz: “ At the time of partition 
the endoplast exchanges its customary granular structure for a 
striate or fibrillate one, assuming its normal aspect again after 
the birth of the embryo.” I was not, however, able to obtain 
any evidence of such change; the characteristic granular ap- 
pearance remained throughout. Many embryos were seen to 
escape; as indicated in the figure 4, which represents an optical 
section, the extrusion takes place at the anterior surface sur- 
rounded by the four anterior marginal lobes. The partition is 
