184 BULLETIN OF THE 
contractile portion. If now we conceive this plasmatie portion to be 
reduced to a minimum, the form of muscle cell characteristic of Gordius 
will be reached; for in this genus the projecting protoplasmic portion is 
entirely lacking, the layer of contractile fibrille surrounds the entire 
cell, and the nucleus is found in the thin strip of plasma which occu- 
pies the centre. Not only do we find in a typical Coelomyarian cells 
in which the plasmatic cell body hardly projects beyond the contrac- 
tile layer, but I have also been able to find in cross sections of Gor- 
dius sp.? certain regions where the fibrillar layer in the proximal 
portion of the cell differs in thickness and in refractive power from that 
in the distal portion. I do not believe, therefore, that the difference in 
the muscular systems is so great as has been maintained. 
To consider the second objection urged by Biirger against the rela- 
tionship of Gordius and Nectonema, namely, the structure of the intes- 
tine, it will be necessary to make a short digression to consider the 
structure of the alimentary canal, and especially of the cesophagus, in 
Nematodes. Most text-books recognize only one type of cesophagus in 
this group, a muscular organ with a more or less triangular lumen 
lined with chitin, from which muscle fibres radiate perpendicularly 
to the long axis of the tube. This organ evidently acts like a suction 
pump in taking up nourishment. 
If, however, one examines the literature on the group, it is evident that 
there are a number of families to which this description will not apply, 
and that there is really a second well marked type of esophagus. This 
consists of a minute chitinous tube extending through a cell, or row of 
cells, with which no muscle fibres are connected. Evidently there is here 
no means of varying the size of the lumen. I believe the wsophagus in 
every family of Nematodes may be reduced to the one type or the other. 
The larger number of forms show the first, but in the Trichotrachelide 
and Mermithidz the oesophagus is constructed on the second type, as is 
also the case in Nectonema. In Gordius this organ is found to be highly 
degenerate, and in certain species, or in specimens of a certain age, has 
entirely disappeared. Its condition appears to be different according to 
the descriptions given ; but in a specimen collected in Cambridge there 
is absolutely no trace of an csophagus in a perfect series of transverse 
sections. From the account of Vejdovsky (’86, p. 404) it is at once evi- 
dent that the csophagus does not belong to the first type, and according 
to his description! and figures (’86, p. 404, Taf. XV. Fig. 35) it bears a 
1 Vejdovsky says (p. 404) : “ Als Mundhdhle bezeichne ich das enge Kanilchen,” 
ete. It is this portion of the alimentary canal which I regard as the morphological 
equivalent of the esophagus of the second type. 
