C. L. Boulenger 
139 
found in fresh faeces, although earlier stages were occasionally met 
with. The egg contents are dark in colour, opaque and filled with coarse 
yolk granules; the vitelline membrane is usually conspicuous. 
Development of the Egg outside the Host. 
The development of Nematodirus has received little attention from 
previous investigators. Ransom (1911) seems the first to point out that 
the embryo within the egg-shell develops into a larva with the filariform 
type of oesophagus before hatching, thus differing from other Strongyles, 
such as Haemonchus contortus, in which the newly-hatched embryo 
possesses a rhabditiform oesophagus with a posterior bulb, not developing 
into the larval stage with filariform oesophagus until later. Railliet 
and Henry (1912) confirm this statement and add the information 
that the embryo undergoes two moults within the egg-shell before 
hatching. Maupas and Seurat (1913) describe the early development 
in more detail and figure the newly-hatched larva; they show that the 
latter is provided with a sheath formed by the second ecdysis and that 
the skin cast during the first moult can also be seen surrounding the 
mature larva within the egg-shell. 
In order to study the development outside the host it was necessary 
to obtain eggs in large numbers and, as far as possible, in pure cultures, 
i.e. free from the eggs of other parasitic or free-living Nematodes. 
Such cultures could be obtained from two sources: (a) from the sexual 
organs of the adult worms, (6) from the fresh faeces of infected sheep. 
A certain number of cultures were made by teasing up the bodies of 
mature females; by this method, however, the eggs obtained were not 
numerous, moreover they included a very large percentage which failed 
to continue their development; it was, therefore, found more con¬ 
venient to obtain the material from the second of the two sources 
just mentioned. 
From the fresh faeces of heavily infected sheep eggs could be obtained 
in very large numbers by the usual methods of sieving and sedimenting 1 : 
by the use of very fine sieves it was found possible to separate the large 
Nematodirus eggs from the smaller ones of other genera. 
The eggs of Nematodirus filicollis were found to develop equally 
well in tap-water and in moist faeces, in the case of the faecal cultures 
it was found necessary to provide sufficient aeration in order to prevent 
the “poisoning” of the eggs by decomposition products. Eggs in water 
1 For a comparative account of the methods of examining faeces cf. HaE (1911). 
