28 MORGAN. VoL. dx: 
from the body-cavity. One of these horns is shown in Fig. 4, 
at the side of the stomach. 
A careful examination shows that at this stage no trace of 
the proboscis vesicle is present. Neither the second (collar) 
body-cavities nor the third (posterior) body-cavities are repre- 
sented. 
Passing to Stage 2, represented in Fig. 2, Pl. I, we gather 
from serial sections, both cross and longitudinal, the following : 
The ectodermal cells of the body wall are more flattened than 
in the preceding case, although the same distinction between 
the thickness of circum-oral and extra-oral regions is to be 
found as before. 
A part of a longitudinal section, showing a portion of the 
lateral wall, is given in Fig. 6. The most conspicuous feature 
of such a section is the row of large cells forming the circular 
ciliated band. A group of three or four large cells, with 
flagella-like processes, form the band. Each cell has a single 
large cilium (or flagellum) that is split up into fibres by the 
hardening fluids. Above this region, the ectoderm of the 
extra-oral area is considerably thickened ; higher up, the lower 
limb of the circum-oral band is cut, and above this the section 
passes through the circum-oral area. The posterior plate is 
cut in the lower portion of the figure. Its most noticeable 
feature is! the) presence ,of .a, ciliated: resion ‘cut acrosstaim 
the section; this forms a circle of small ciliated cells on 
the posterior plate. It was also undoubtedly present in the 
preceding stage. 
Surface preparation of portions of the larva verify the facts 
just recorded, but did not seem of sufficient importance to 
warrant separate figures. The nuclei of the circum-oral area 
are nearer together than in the extra-oral area. In the latter 
area, collections of nuclei are found around large, clear area, as 
shown in Fig. 7. 
One side of the apical plate in surface view is shown in 
Fig. 7. On each side the anterior ciliated band is seen to end 
in two free ends. A pair of eyes (one in figure) are found in 
the apical plate. Each is situated not in the centre of the 
