THE EGG-PRODUCING CAPACITY OF ASCARIS 
LUMBRICOIDES 1 
By Eloise B. Cram 
Zoological Division , Bureau of Animal Industry , United States Department of 
Agriculture 
INTRODUCTION 
In connection with the life history 
of Ascaris lumbricoides, concerning 
which there have been important 
developments in recent years as a 
result of the researches of Stewart 
and other investigators, the question 
of the capacity for egg production is 
of considerable interest. It is well 
known that this worm is very fertile, 
but a great deal of uncertainty exists 
as to the number of eggs that a female 
may produce, the various estimates 
in the literature ranging up to as many 
as 80,000,000 eggs. The writer has un¬ 
dertaken to make an approximate count 
of the number of eggs, fully developed 
and in process of development, in the 
female Ascaris. Various investigators 
(Cloquet, 2 Eschricht, 3 Siebold, 4 Leuc- 
kart, 5 and others) have described the 
reproductive system of the female 
Ascaris lumbricoides , with more or less 
completeness, and only a brief review 
of certain aspects of its anatomy, 
important in relation to the question 
of capacity for egg production, need 
here be given. 
SEN ORGANS OF FEMALE ASCARID 
The two uteri branch off from the 
vagina at its inner end about 6 
mm. from the vulva. Bakker 6 con¬ 
cludes from the study of numerous 
specimens that as the body length 
becomes greater the uterine length 
does not increase proportionately. She 
found that whereas ascarids 19 and 20 
cm. long contained uteri 17 and 18 cm. 
in length, respectively, ascarids 32 
and 35 cm. long had uteri 22 and 24 cm. 
in length, respectively. The uteri 
lie in a fairly straight course backward 
from the genital pore, the distal 
portion of each turning forward. At 
this distal end is situated the receptac- 
ulum seminis, beyond which is the 
oviduct and then the long filiform 
ovary which coils back and forth in the 
body cavity to such an extent that a 
cross section of the body shows 20 or 
30 sections of the genital tubes. Each 
ovary measures 120 to 200 cm. in 
length, five to eight times the total 
length of the worm itself. 
A histological study of these various 
sex organs of the female ascarid shows 
the steps in the development of the 
ova. The extremely delicate free or 
distal portion of the ovary (about 
225 u in diameter) is the germinal zone; 
it contains a mass of protoplasm with 
an abundance of nuclei, or germinal 
vesicles, scattered through it. At a 
distance somewhat farther from the 
free end of the ovary, the protoplasm 
gradually forms around the vesicle and 
distinct cells or ova begin to appear 
(fig. 1). Then follows the develop¬ 
mental zone of the ovary, in which the 
ova have elongated and arranged 
themselves in wreaths around a rachis, 
an axial protoplasmic cord which 
supplies them with nutriment. The 
ova are from 100 to 200 u in length, and 
as viewed in a longitudinal section of 
the ovary are 9 to 10 u broad at the 
outer end and somewhat narrower at 
the inner end, which is attached to the 
rachis (fig. 2). In cross section of the 
ovary they are about 7ju broad at the 
outer end and sharply pointed at the 
attachment to the rachis (fig. 3). The 
germinal vesicle is situated near the 
broad end of the ovum in its early 
development, when the ovum has a 
length of 100 m (fig. 4), but later it 
gradually approaches the center, at 
1 Received for publication August 22, 1924; issued July, 1925. 
2 Cloquet, J. anatomie des vers intestinaux. 130 p., illus. Paris. 1824. 
3 Eschricht, D. F. inquiries experimental and philosophical, concerning the origin of 
intestinal worms. Edinb. New Phil. Jour. 31: 314-356, illus. 1841. 
4 Siebold, K. T. von. zur entwickelungsgeschichte der helminthen. In Burdach, K. F., 
Die Physiologie als Erfahrungswissenschaft. Aufl. 2, 2: 183-213. Leipzig. 1837. 
5 Leuckart, R. die menschlichen parasiten. Bd. 2., illus. Leipzig und Heidelberg. 1876. 
6 Barker, C. R. over de identiteit van ascaris lumbricoides en ascaris suilla. Tijdschr. 
Vergelijk. Geneesk. 6: 160-230, illus. 1921. 
Journal of Agricultural Research 
Washington, D. C. 
( 977 ) 
Vol. XXX, No. 10 
May 15, 1925 
Key No. A-75 
