i 4 4 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
width of the organism. The body of the parasite is markedly striated, the margin in 
profile showing a double contour, due to the presence of a very fine enclosing 
membrane. This membrane is very well seen at the anterior and posterior extremities. 
The tail tubercle is still present but only measures about 2/x in length, and appears 
very minute in proportion to the body of the organism. Besides these external 
structures, the position of the anal aperture is easily made out, situated a little way 
from the tail end on a slight prominence, generally there is seen extruded from the 
aperture a large highly refractile granule. In some organisms a slight papilla is seen 
some little way from the head end on the same border of the parasite as the anal 
tubercle. The internal structure of the parasite shews very clearly the differentiation 
mentioned in the previous stage of its metamorphosis ; the outer layer consists of 
probably two or more layers of cells, the innermost being formed of cubical shaped 
cells have rather large nuclei (See Fig. 6). The internal granular layer is seen to 
have become developed into what is evidently the future alimentary canal. This 
commences at the anterior end of the organism, at a small terminal papilla, as a 
narrow tube piercing the outer cuticle and continuing on as a comparatively thick 
column of cells running down the centre of the body. There is an obvious thickening 
in this column of cells at about one-third the length of the worm from the anterior end. 
Opposite the anus there is again a large thickening of this cell column, in which 
highly refractile areas are generally seen. The column of cells now narrows again to 
form a rather wide tube ending on the anal tubercle. In some parasites this internal 
cell layer is easily seen to be in reality a cellular tube running down the length of the 
body. Between the cuticular and alimentary cell layers a space is generally seen — 
the body cavity. Opposite the anterior lateral papilla a highly refractile rounded area 
of small cells is observed in some parasites (Fig. 7). It is probable that from these 
cells the future uterus and ovary or spermatic canal, as the case may be, arises. A 
little anterior to the genital papilla in some specimens a band of small cells can be 
made out crossing obliquely the anterior part of the intestinal canal, this band repre- 
sents the nerve collar (Fig. 7). In this stage the worm is still in the fat body, it 
shows slight lateral movements when dissected out. 
The following are some measurements at this stage : — 
Total length 
Length to nerve 
collar ' 
Length to 
genital papilla 
Length to 
anus 
Central 
width 
Width at 
nerve collar 
Width at 
genital papilla 
Width at 
anus 
■+V4+M 
Not distinct 
22-62 [A 
.33-66 
2 9"3 + 
1 89-06 
2771 
Not seen 
16952 
2 ^34 
2 9'34 
26-08 
24776 
35-86 
65-2 
235-76 
32-6 
29-3+ 
32=6 
26-08 
