1887] Embryology. 197 
ressed, 2.72 mm. Proboscides, four, very long, slender, cylin- 
drical, and armed with recurved hooks of different sizes. The 
proboscides were not entirely everted, but by counting the series 
of hooks which are exposed, and allowing for the part which is 
inverted, which can be plainly seen through the transparent walls 
of the proboscis, the result is about one hundred series of hooks 
arranged in spirals. The spirals are nearly 0.05 mm. apart, and 
the proboscides about 4.80 mm. in length. There are about fif- 
teen longitudinal rows of hooks. These rows do not coincide 
exactly with the axis of the proboscis, but make about one and 
a half turns around it from base to apex. The hooks in these 
longitudinal rows present Be following differences. (Fig. 6. 
Three contiguous rows have small, recurved, stoutish hooks, 
which lie in groups of two, one hook noia ey in front of the 
other, and each group of two thus formed corresponding in 
position with a single hook in each of the other longitudinal 
series. The central of these three rows does not have the hooks 
as distinctly placed in groups of two as the two remaining rows. 
t the bases of the proboscides these hooks are 0.0152 mm. in 
length, increasing to 0.02 mm. at the apex, gas e breadth of 
base 0.0102 mm. throughout the series. On e side of this 
group of three longitudinal series lies a series of pb slender, 
slightly recurved hooks, These hooks are 0.0127 mm. in length 
at the base of the proboscis, increasing to 0.02 mm, at the apex, 
with the breadth of base 0.0076 mm. Each hook of these two 
series corresponds in position to one of the groups of two in the 
three series first mentioned. e remaining series of hooks are 
ten in number. It is rather difficult to estimate the exact num- 
ber of these longitudinal series, since the transverse spirals are 
not in even curves, but have a slight zigzag or sinuous course, so 
that the exact number of longitudinal series in a given part of 
the circumference is not always Plainly: shown. In one proboscis 
I counted eleven of these series, but in another, of which I had 
a plainer view, there were certainly but po These hooks are 
much larger, stouter, and more sharply recurved than those in 
the other series.- The length of one of the largest near the base 
of the Sokoi was 0.0356 mm., with a breadth of base of 
0.0254 mm. Towards the apex of the proboscis they are a little 
longer than this. These larger hooks are not of uniform size, 
those adjoining the smaller longitudinal series being smaller than 
course standing side b 
The e Ge (Fig. 4) are long and spiral. A con- 
tractile ligament was clearly defined in each and could be traced 
out into the proboscis, where it appeared as a tubular band con- 
taining a fluid in which floated a few granules. Towards the end 
