570 Cutn PING 
In addition to the two just mentioned, another one is found in the ninth 
segment. This commissure, however, is not so large as the anterior one 
and it might easily be confused with some of the inner branches from 
the trunks. 
As the larva is amphipneustic, each dorsal trunk has its anterior and 
its dorsal spiracles. The anterior spiracles are lacking in the young 
larva during the first instar. The anterior spiracular process consists of 
a hand-shaped body bearing four digits, although sometimes only three 
are present. Each digit has a small opening at the tip (Plate LIV, 6). 
The posterior spiracles are found in the larva shortly after hatching. At 
this time, the caudal process, however, is not well developed. At the 
caudal end there appear two oval disks (Plate LIV, 4), which become the 
tips of the future caudal branches. In the center of each disk are two 
metallic shining chitinous knobs with a small round pit closely mesad 
to each of them. The spiracles are in the center of these knobs. When 
the iarva is mature, the flat disk develops into a conical cap and each 
of the knobs breaks up into two parts, thus making four al] together on 
each cap surrounding a large round pit in the center. There are four 
curved grooves around these knobs (Plate LIV, 7), distinctly delimiting the 
discontinuation of the chitin at the tip of the cap. The central pit is 
bordered with four fan-shaped chitinous membranes which Tragardh calls 
“ chitin blatter.”” These membranes are outspread when the caudal tips 
come to the surface for breathing, but each becomes folded longitudinally 
to cover over its spiracle when immersed. 
Each dorsal trunk has eight pairs of inner branches and ten pairs of 
outer branches. The former are smaller than the latter. The branches 
of the first pair at the fourth body segment of the larva attach to each 
side of the cephalopharyngeal skeleton and there ramify. The branches 
of the second pair originate in the same segment, and shortly after their 
origin each branch divides into an anterior and a posterior sub-branch, 
the former going to the cephalopharyngeal mass, the latter to the ring. 
The third and fourth pairs are found in the fifth and sixth segments, 
respectively, overlying and supplying the proventriculus. Branches in 
each of these two pairs meet each other and are conjoined at their tips, 
thus resembling a commissure. Following this are the fifth and sixth 
pairs in the sixth and seventh segments, respectively. These supply the 
posterior part of the proventriculus, The seventh pair lies in the eighth 
