588 ROBERT MATHESON 



sort of connective tissue. It is penetrated with tracheae, and 

 tracheal end cells with their nuclei are usually found distributed 

 through it. It does not show any of the characteristics of verte- 

 brate connective tissue when stained by the differential stains 

 used by histologists. It may be analogous to the tissue formed in 

 the developing vitreous body of the vertebrate eye. Here recent 

 researches indicate that it is derived from the prolongations of the 

 cells of the retina, therefore ectodermal in origin. In the case of 

 Corydalis this so-called connective tissue stains in the same way 

 as the basement membrane and one can readily trace out into it 

 prolongations of the epithelial cells. The vacuolate condition in 

 the cells near the basement membrane indicates a secretion. If 

 the basement membrane be considered as a product of the epi- 

 thelial cells I think there is no evidence to show that this supposed 

 connective tissue is not also a secretion of the epithelium. This 

 tissue is widely distributed throughout the intestine and may 

 be referred to under the non-committal term of supporting tissue. 



The fore-gut between the gizzard and the oesophageal valve 



At its posterior end the gizzard gradually passes into a short, 

 cylindrical tube. The interior of this tube presents internally a 

 thick, chitinous lining without teeth-like processes. Near its pos- 

 terior end are found four large, chitinous ridges projecting into 

 the lumen (fig. 12). These large ridges extend into the anterior 

 end of the mid-intestine and form part of the oesophageal valve. 



Arrangement and action of the muscles 



The longitudinal muscles, running in an oblique manner and 

 forming a net-like cylindrical ring around the oesophagus, group 

 themselves into six bundles at the beginning of the gizzard (fig. 3). 

 These six bundles pass respectively under the six large longitu- 

 dinal folds and attach themselves to the bases of the anterior 

 teeth. At a point just cephalad of that where these muscles are 

 attached, there arise six other longitudinal muscles which run 

 caudad and are inserted on the anterior elongated bases of the 

 posterior teeth. The fibers of these two sets of muscles form a 



