52 PATIEN: [Vo.L. XII. 
the oesophagus and first two pairs of appendages, and the 
drawing together of the appendages of the fourth pair. 
In Fig. 46 is a more typical condition. The cephalic lobes 
are entirely absent, and the anterior limbs of the thoracic 
margin are converging to form the apex of an inverted V. 
The chelicerae have united at ck., and the second pair of 
appendages forms a single, long, coiled and slender process, af?. 
The third pair has almost fused, but each appendage still retains 
its characteristic shape. 
In Fig. 44 the second and third pairs have united, while 
every trace of the cephalic lobes and of the chelicerae has 
disappeared. In Fig. 42 about the same change has taken 
place, except that the degeneration of fused appendages has 
progressed farther backwards, for here both the chelicerae and 
second pair of appendages have disappeared. The fusion of 
the appendages of the fourth pair is not quite completed. 
Fusion accompanied by degeneration of the two anterior pairs 
of appendages is shown in Figs. 43 and 49. In Fig. 48 fusion 
and antero-posterior atrophy have given rise to a form frequently 
seen in which little of the embryo but the three posterior 
thoracic appendages is left. In Fig. 41 is a similar embryo in 
which the oesophagus is still visible a long distance in front of 
the embryo. It is a pit-like depression merging gradually into 
a long cloud of cells lying below the surface, and extending 
backward toward the embryo, doe. These cells represent 
either the degenerating remnant of the anterior portion of the 
embryo, or of the oesophagus. 
If the process of fusion and degeneration progresses in the 
way the various stages just described indicate, we should obtain 
embryos in which all the paired organs have been fused and 
subsequently absorbed, except the last pair of appendages, or 
perhaps the tip of the tail. This appears to be the case with 
the one in Pl. IX, Fig. 106. We should not forget that 
this embryo has been developing as long as the others here 
described ; and that it really is in a late stage is shown by its 
size, and by the concrescence of the posterior limbs of the 
germinal area back of the median appendage or lobe. There 
is no trace whatever of a nervous system, unless the dark area 
