148 
Heligmosomum muris Yokogawa 
body extending a little in front of the excretory pore and connected with it 
by a short duct. The cervical glands could be very clearly distinguished in the 
living larvae of the parasitic stages, although they were difficult to see in the 
sexually mature worms. In the specimens from the experimental rats 15 to 
20 hours after infection, the protoplasm of the cervical gland cells is not 
granular while in later stages it contains many granules. These gland cells 
(Fig. 7, Plate VIII and Text-fig. 3 a and b) are located in the dorsal body-cavity 
and extend along the dorso-lateral sides of the chyle intestine. The anterior 
ends of the cervical glands are narrower than their posterior ends, and they seem 
to be connected with the ' k bridge ,: as Looss (1905, pp. 104 and 105, Fig. 30) 
shows in Ancylostoma duodenale at the ventra-lateral side of the oeso¬ 
phagus. 
These cells have an elongate lancet shape, and extend to about the middle 
of the body. They contain large transparent ovoidal nuclei, which he in the 
centre of the glands. Each nucleus has a round nucleolus. As the reproductive 
organs extend forward in development the cervical gland cells become more 
difficult to see since they are crowded to the side by the anterior part of the 
ovary or the testis as the case may be. 
3. Sexual Differentiation and the Development of the 
Reproductive Organs. 
(a) General Discussion. 
The post-embryonic development of the reproductive organs of nematodes 
is very insufficiently known. H. muris offers very good material for the study 
of these organs since they are simple in this species and the period of develop¬ 
ment is short. Therefore an especially careful study was made of the repro¬ 
ductive organs and a very large series of stages was examined. 
The stage of development of the reproductive system does not always 
depend on the time elapsed after infection, but rather is correlated with the 
degree of growth in size. There are of course some variations in the develop¬ 
ment of this system in animals of about the same size. I will describe the 
average condition which has been ascertained from a very large series of 
specimens. 
Looking in the literature on the development of the nematodes, nothing 
is known particularly regarding the development of the internal and the 
external sex-organs, while in the higher animals they develop from two 
different origins, one part from the genital anlage, while the other without 
reference to the genital primordium. Neuhaus (1903) who investigated the 
post-embryonal development of the Rhabditis nigrovenosa described that the ; 
vagina might be developed from the middle part of the genital primordium, 
while Leuckart (1887) described that the vagina of Allantonema is formed by 
a projection of the ventral wall. The argument of Neuhaus is based on the 
position of the vagina in the body and the identity of the cells. 
