30 
Fig. 8. Anterior and posterior ends of late second- 
stage larva. 
An excretory pore and a large excretory 
cell were plainly visible on the ventral side of 
the esophagus, 250-300 ju from the anterior 
end. 
The nerve ring and several small ganglion 
cells encircled the esophagus, about 100 n 
anterior to the excretory pore. 
The genital primordium was visible in the 
living larvae ventrad of the intestine, approxi- 
mately 500 ju from the anus. 
PACIFIC SCIENCE, Vol. V, January, 1951 
Third-stage larvae 
Third-stage larvae varied from 7.53 mm. to 
8.31 mm. in length and had a maximum width 
of approximately 157 ju. Other than in this 
feature, their over-all appearance was much 
the same as that of the second-stage larvae. 
The cuticle was smooth and no striations 
were discernible, either transverse or longi- 
tudinal. The anterior oral opening was six- 
lobed, and four sublateral papillae were 
plainly visible projecting at right angles to 
the surface. No caudal papillae were present 
in this stage. 
The esophageal gland-like structures ap- 
parent in the second stage were not discerni- 
ble in the third-stage larvae, but a number of 
cells were seen to surround the esophagus at 
its anterior end. The esophagus was distinctly 
divided into an anterior muscular portion 
having a length of about 210 n and a pos- 
terior glandular portion approximately 600 /x 
in length. The remainder of the alimentary 
TABLE 7 
Measurements of Third-stage Larvae* 
Days after infection 51* 
Lengthf 7.53-8.31 
Width (ant, end) 53.5 
Width (max.) 157 
Width (at anus) 92.3 
Buccal capsule length. 35.7 
Esophagus length. . 846 
Esophagus width (post, end) . 71.5 
Intestine width (max.). 107 
Nerve ring from ant. end 178.5 
Excretory pore from ant. end 303 
Anus to post. end. 184 
*In intermediate host. For measurements of third- 
stage in definitive host, see Table 7. 
fThis measurement in millimeters; all others in mi- 
crons. 
tract appeared much the same as that of the 
second-stage larvae. 
In addition to the excretory pore and cell 
apparent in the second stage, two lateral ex- 
cretory canals were traced from the region 
anterior of the excretory pore to very near 
the tip of the tail. Each canal sent off an 
anterior branch which joined ventrad of the 
esophagus and entered the excretory cell as a 
common excretory duct. The lateral canals 
