NOTES AND DESCRIPTIONS OF SOME PARASITIC HELMINTHS 4895 
larva, coiled in the form of a figure 8, was found in each cyst. The larvae measure 
5.¢ mm. in length and the greatest breadth is 0.22 mm. The body, which is 
finely striated, tapers toward each extremity. The anterior extremity is obtuse 
and bears two lateral cuticular elevations or prominences, 7u high, each with a 
minute denticle-like serration on its internal, or oral aspect (No. 399, Fig. 8). 
The posterior extremity, which is slightly incurved, bears a hemispherical knob 
ornamented with two to three rows of blunt spines (No. 399, Fig. 9). There 
appear to be four submedian cephalic papillae. The funnel-shaped buccal cap- 
sule, 34u long and 9u at its widest point, has thick cuticular walls. The oesoph- 
agus, typically spiruroid in character, is divided by a well-marked constriction 
into a glandular anterior part, 0.28 mm. long, and a muscular posterior portion 
1.7 mm. long. The nerve ring encircles the glandular part of the oesophagus 
0.2 mm. from the head extremity, and the excretory duct opens ventrally 0.84 mm. 
from the anterior extremity. The intestine discharges by a short narrow rectum 
at the anus, about 60u from the caudal extremity. Several unicellular, gland-like 
structures are found in the caudal region. No rudiments of developing gonads 
were observed. 
The specific identity of the parasite described above cannot be determined 
because of its larval condition, but it evidently belongs to the Spiruroidea. The 
life-cycle of the few spiruroid nematodes that have been worked out, have all 
involved an “‘intermediate”’ insect host, which, having ingested the embryonated 
eggs of the parasite, are found to harbor second stage larvae encysted in their 
muscles or viscera. When the insect host is eaten by the proper vertebrate host, 
the encysted larvae are liberated by the digestive juices of the stomach or in- 
testine, and proceed to develop to maturity in various locations. However, 
should the larva become liberated in an unfavorable or foreign host, reencyst- 
ment, usually in the walls of the alimentary tract, often takes place without any 
further development. Such a state of affairs was noted by Cram (1924) ' who, 
on feeding encysted larvae of a form resembling Physocephalus sexalatus, occur- 
ring in certain dung beetles, to the frog, pigeon, and guinea pig, found that the 
larva reencysted. Recently Faust ? (1927 and 1928), working in Pekin, noted 
that the larvae of Spirocerca sanguinolenta found in a beetle (Canthon sp.) re- 
encysted in the mesentery, omentum, parietal wall of the stomach, ete., when 
eaten by an unproper host, a hedge hog, but developed to maturity when fed to a 
dog. The presumption that the encysted parasite in the mongoose represents a 
third-stage larva of a spiruroid which has been introduced into an improper 
host appears legitimate. Such larvae usually encysted in insects (cockroaches, 
beetles, etc.) have been repeatedly described but, without recourse to confirma- 
tion of the diagnosis by the experimental method, it is both unsatisfactory and 
undesirable to attempt to identify them specifically or even generically, since 
in their ontogeny the larvae of different genera exhibit many points of anatomical 
1 Cram, E. B.: Jour. Parasit. (1924), XI, 117. 
2 Faust, E. C.: Migration route of Spirocerca sanguinolenta in its definitive host. Proc. Soe. Exp. 
Biol. & Med. (1927), XXV, 192-194. The life cycle of Spirocerca sanguinolenta — a natural nematod 
parasite of the dog. Science, n. ser. (1928), LXVIII, 407-409. 
