354 WHEELER. [Vor. III. 
inent in #/atta, viz. the appearance of appendages on the 
abdominal somites. There are not the slightest traces of even 
the pair of appendages of the first abdominal somite, which in 
Blatta develop into the large glandular organ of which I have 
treated elsewhere (50). The tracheal invaginations are situated 
at the bases of the legs. Those of the first thoracic segment 
are small, and soon close over and disappear. The second pair, 
which are almond-shaped, are the largest in the whole embryo, 
and so remain. They are situated near the constriction divid- 
ing the first from the second thoracic segment, and in later 
stages often have the appearance of belonging to the first seg- 
ment. The metathoracic invaginations are somewhat smaller, 
and are also placed near the edges of the somite to which they 
belong. In the succeeding abdominal segments there is a 
tracheal invagination in the middle of each lateral half. These 
invaginations become successively smaller till they can be de- 
tected only with great difficulty on the 1oth and 11th somites 
(¢ 19, 220). The 11th somite is followed by the broad subhex- 
agonal caudal plate with its large protodzal invagination. The 
corners of the plate are formed by rounded lobes containing 
apparently spherical bodies, the ends of the three pairs of Mal- 
pighian vessels. These grow off from the protodzum at an 
unusually early period in Doryphora, and turn back till their 
rounded blind ends terminate just beneath the surface ecto- 
derm. The paired ganglionic thickenings are seen in the 
embryo figured to be slightly kidney-shaped with their hili 
directed laterally. The J/tttelstrang is apparent in the small 
and nodular intersegmental thickenings (sz), which appear 
from the surface as small masses of cells of a somewhat dif- 
ferent nature from those of other portions of the median line. 
The surface changes which the embryo undergoes in the 
stages immediately following that represented in Fig. 72 may 
be briefly summarized. The embryo just described lies like a 
band on the ventral yolk, the caudal portion still extending 
round the hind pole of the egg, and up the dorsal surface a 
short distance. The isochronous changes which ensue are, (1) 
a shortening of the embryo, bringing the tail to the pole of the 
egg; (2) a broadening of the embryo, the sides of which now 
bend dorsally and clasp the yolk; (3) a greater concentration 
of the cephalic, mandibular, and maxillary somites to form the 
