144 PATTEN. [Vou. XII. 
EXPLANATION OF PLATE X. 
FIG. 100, X 25. This is one of the oldest double monsters seen. It should be 
compared with Figs. 96 and 98. The development of the new halves had appar- 
ently not separated the oid ones much more than in Fig. 98. The main embryo has 
the abdomen of the original embryo. 
In the smaller embryo are two unpaired, tongue-like, abdominal appendages. 
The appendages of the sixth segment are fused at their base, and in front of 
them is a row of three long, crumpled filaments, representing the medianly fused 
appendages of the third, fourth, and fifth segments. All the segments in front 
of the third have disappeared. 
Fic. 101, X 30. Same embryo as in the preceding figure, seen from above. The 
dorsal surface of the thorax of the smaller embryo is spread out on that of the 
larger. Below the dark mass of cells that represent the remnants of the thickened 
margin of the mesodermic area is an elongated cloud of cells, probably the remnant 
of the oesophagus, ge. 
There is a well-developed heart in the abdominal region of the larger embryo, 
but none in that of the smaller one. 
FIG. 102, X 30. There are three embryos on this egg. Embryo 4 is normal 
and perfect in everything except the abdomen. JZ has undergone median fusion 
and degeneration, and transverse fission. The cephalic lobes and first four segments 
have disappeared, except two incompletely fused appendages. The abdomen and 
the posterior part of the thorax persists. The latter is bounded in front of the 
fifth pair of appendages by a great fold that extends completely across the median 
line. The nerve-cord in this posterior remnant of an embryo forms a conspicuous, 
unpaired ridge. 
Embryo C has undergone such fusion and antero-posterior degeneration that 
nothing remains but the fused appendages of the sixth segment, and a rudimentary 
abdomen. 
It is probable that the original embryo divided lengthwise, giving rise to 4 and 
B&C, and the latter then divided, giving rise to B and C. 
FIG. 103, X 30. In this triple embryo the individuals, 4, 4, and C, were proba- 
bly produced in the same way as in the preceding. As all the embryos could 
not be seen at once, each embryo was drawn separately with the aid of a camera, 
and finally all three united and represented as though spread out on a flat surface. 
Embryo 4 has undergone median fusion and transverse fission. The fused 
appendages of the first four segments are arranged in a single row; it is very 
rarely that one sees as many unpaired appendages as this. 
The cephalic lobes are narrowed, and covered by a hood-like fold of ectoderm, 
through which one sees the oesophagus. 
The marginal fold has grown across the median line in front of the fourth pair 
of appendages, as in the extreme forms of hour-glass embryos. In front of this 
fold, and near the median line, are the dorsal organs. 
The fifth pair of appendages have not fused entirely. Embryo & has degen- 
erated completely in front of the fused fifth pair of appendages, with the exception 
of the dorsal organs, which have almost reached the median line. 
The sixth pair of appendages have nearly fused at the base, but are distinct at 
the tips. 
