SOME OBSERVATIONS ON ACINETARIA. 365 
In an embryo (text-fig. 4) which left its mother at 10.45 p.m., 
the movements became very slow at about midnight, and it 
was fixed at 2 a.m. At this period the cilia had not yet 
disappeared, but the commencement of the stalk was already 
to be seen. 
A slightly later stage of the development is seen in text- 
fig. 5,in which the stalk had almost attained its definitive 
length, and the cilia have disappeared. At a still later stage 
the tentacles make their appearance scattered irregularly 
TEXT-FIGURE 5.—A. papillifera soon after attachment, show- 
ing disappearance of cilia and development of stalk. (Zeiss 2 mm. 
apochr., comp. oc. 6.) Ma. Macronucleus. S¢. Stalk. 
over the surface of the body, and the theca develops as a 
cup surrounding the body at its junction with the stalk. 
Finally, the superfluous tentacles are withdrawn, and the 
animal becomes compressed laterally, assuming the shape of 
the fully developed form, the theca growing up to surround 
the whole body with the exception of a slit at the apical 
extremity, through which the lateral lobes bearing the tenta- 
cles protrude, and the ciliated embryos escape. 
Conjugation.—As regards the early details of conjuga- 
tion, there is no doubt that they agree with Maupas’s general 
scheme for Ciliates (Scheme I). 
In preparations of the later stages the small size of the 
micronuclei, and the large number of chromatin-masses 
