54 PATTEN. [Vor. XII. 
in Pl. VIII, Fig. 98, also in Pl. IX, Figs. 102 and 103. See 
also pages 67—71. 
The ordinary antero-posterior fusion is well shown in Fig. 94, 
where the left-hand embryo consists merely of a tail, the nor- 
mal fifth and sixth, and the fused fourth, pairs of thoracic appen- 
dages. A mere trace of the anterior part of the embryo is 
shown at oe., and the well-developed approximated dorsal 
organs are clearly seen at do. No nervous system or other 
organs are visible. In the upper embryo of Fig. 97 fusion and 
complete degeneration of the anterior end of the embryo are 
shown. ‘The fourth pair has fused and is much reduced, the 
fifth is fused and very long and much folded, the sixth pair 
is approximated, but not fused. In the opposite embryo the 
process has gone on a little farther, resulting in the fusion of 
the fifth and sixth pairs. The fourth pair was very small and 
partly concealed under the folds of the long and much crumpled 
fifth pair. The dorsal organs in the upper embryo are close 
together, in the lower they are completely fused, do. 
Still another condition, but similar to that in Fig. 97, is 
shown in the right-hand embryo of Fig. 96. There is no mar- 
ginal fold here or any dorsal organ. The tail has been thrown 
outwards, making a sharp bend in the longitudinal axis, just in 
front of the sixth pair of legs. The latter is nearly fused; the 
fourth and fifth pairs completely so. I can form no plausible 
conjecture as to what the process to the left of the left flabellum 
may represent. It is entirely out of place as an appendage, so 
far as we may judge from the other cases. It is important to 
observe that in Fig. 96, and in both embryos in Fig. 97, the 
flabella are larger than usual in embryos of this age, resem- 
bling, except in position, normal thoracic appendages. The 
problematical appendage of Fig. 96 may be an extra flabellum 
belonging to the left fifth thoracic appendage. But no indi- 
cation of such an organ has ever been seen in any other 
specimen, 
In the curiously aborted embryo seen in Fig. 100, the 
posterior three or four (?) pairs of thoracic, and two or three 
abdominal, appendages are fused along the median line. Here, 
all three thoracic appendages show about the same increase in 
