330 AUSTRALIAN HIRUDINEA, I., 



from the main portion of the pouch. The caeca are directed 

 towards the ventro-lateral region of the body. They increase 

 in size and importance as they approach the posterior end of 

 the body, the smallest pair being most anterior, the largest 

 most posterior. The first five pairs are simple in outline, but the- 

 sixth pair gives rise to a great number of secondary caeca, and 

 extend on either side of the stomach from the forty-fourth to the 

 sixtieth annuli. The walls of the crop and caeca consist of a 

 lining epithelium of large columnar cells, with conspicuous- 

 spherical nuclei, and an external inconspicuous layer of circular 

 muscle fibres. The structure of the walMs such as would best 

 serve the crop and caeca in the function of storing food material. 

 The longitudinal muscles, so strongly developed in connection 

 with the oesophagus, are not represented in the crop and caeca. 



The stomach gives off four pairs of diverticula which are 

 auricular in shape and not elongate as in Glossiphonia heteroclita. 

 The contents of the stomach are quite different from those of the 

 crop. Whereas, in the crop, there is present a mass of muscle 

 material, etc., obtained by the carnivorous character of the 

 species, in the stomach there is found a clear mass as the result 

 of digestive changes. The passage of the material from the crop 

 to the stomach is regulated by a valve-like structure situated at 

 the junction of the crop and stomach. The portion of the crop 

 lying behind the point of origin of the last pair of caeca becomes 

 intimately connected with the antero-mesial wall of the first pair 

 of stomach diverticula; and this portion of the united common 

 wall of the stomach and intestine projects into the cavity of the 

 stomach, preventing material from passing forwards from tho 

 stomach to the crop, and, at the same time, regulating the 

 passage of food from the crop to the stomach. 



The rectum is a pear-shaped chamber opening to the exterior 

 at the anus, which is situated between the sixty-ninth and 

 seventieth annuli. 



The epithelial lining of the stomach takes a very deep stain 

 with hematoxylin. The cells of this layer are tall and columnar, 

 with a spherical centrally situated nucleus. 



