114 PATTEN. [Vox. XII. 
remaining half, which is provided with two distinct appendages, is thrown sharply 
to the left, so that its long axis is at right angles to the rest of the body. 
All the thoracic appendages are present on the right ; but the second and third 
are very large, and the fifth and sixth correspondingly small. On the left, three 
appendages are absent, probably the last three of the series, as the most anterior 
one seems to represent the chelicera. 
FIG. 32, X 60, not sectioned. On the left side the second and third thoracic 
appendages, as in the preceding figures, are unusually large, and the last three 
thoracic appendages are abnormally small. On the right the chelicera is absent, 
and the last three appendages, of which one is entirely absent, are very small. 
The right half of the abdomen is absent, but on the left three appendages and 
their corresponding neuromeres are present. What is left of the abdomen is 
thrown to the right, and its end covered with a large hood-like overgrowth of the 
marginal fold. 
FIG. 33, X 60. Small embryo in stage C. 
Cephalic lobes are very small and partly concealed by the ganglionic fold, 
which nearly reaches to the mouth. Three well-formed appendages, fourth, fifth, 
and sixth (?), are present on the left. On the right the corresponding appendages 
are invaginated, forming three shallow pits, 7.2. The abdomen and the anterior 
part of the thorax are absent. 
The outline of the mesodermic area is visible, showing its thickened rim, wa. 
Its concresced posterior portions form the usual post-anal cloud of cells, 
p-4.c. 
Fic. 34, X 60, not sectioned. A much reduced embryo in stage C. 
The head is turned toward the left, although that side is better developed 
than the right. The cephalic lobes are covered by a distinct, amnion-like fold, 
that extends back to the first remaining appendage. Through the fold may be 
seen the reduced oesophagus. Two appendages are present on the left, and 
corresponding to them on the right, a shallow pit and small papilla. Back of 
these appendages is a large unpaired one, probably formed by the fusion of the 
appendages of the sixth pair. Back of this is a deep furrow, flanked on either 
side by a rounded elevation. 
On either side, just within the limits of the mesodermic area, are two large 
marginal vesicles. 
FIG. 35, X 60, not sectioned. A much distorted and abbreviated embryo. 
The cephalic lobes are broad, and contain a good-sized oesophagus. The 
remainder of the embryo is bent sharply to the right. This is due to the presence 
of three distinct appendages on the left side, and only one (the second?) on the 
right. The tail end of the embryo is invaginated, and covered by a small, over- 
growing fold. The margin of the mesodermic area is clearly defined, and plainly 
shows the notch, due to concrescence of its posterior margin. At the anterior 
end of the embryo is a dark band of yolk cells (?) extending forward to the anterior 
border of the mesodermic area. 
Fic. 36, X 42. Embryo in somewhat older stage than Fig. 29. 
The whole right half is practically normal. The most characteristic feature of 
the embryo is the absence of most of the left half of the thorax ; although the left 
half of the cephalic lobes, and of the abdomen, is nearly normal. 
The whole embryo is somewhat shortened. The appendages of the right side, 
and the right ganglionic fold, extends backwards over the outer surface of the 
