v] 



THE ALIMENTARY AND EXCRETORY SYSTEMS 



105 



the soft inner cuticle in fig. 47 B) takes its place, becoming quickly 

 hardened [145], 



The muscular tunic of the gizzard is excessively strong, owing to 

 the enormous development of the circular muscle-fibres (cm). The 

 longitudinal fibres remain weak, forming only eight or sixteen 

 separate strands (Im) placed externally to the circular tunic. The latter 

 consists of several layers, greatly increased and strengthened below 

 the dental folds, where the fibres run directly inwards towards the 

 cuticle. By insinuating themselves between the columnar cells, 



Cm 



Fig. 47. T.S. through larval gizzard. A. Synlestes weyersi Selys ( x 80). B. Cordu- 

 lephya pygmaea Selys ( x48). cm circular muscle; cu cuticle; cu' soft cuticle; 

 ep raised epithelium; fi fibrillae; Im longitudinal muscle; om oblique muscle; 

 t, t' teeth. Original. 



these fibres become attached directly to the soft inner portion of 

 the cuticle. Such an arrangement is very exceptional, and points 

 to the powerful nature of the operations of this organ. 



For purposes of comparison, a transverse section through the 

 less highly specialized gizzard of Synlestes is shewn in fig. 47 A. 



The Dentition of the Larval Gizzard (fig. 48). 



In the oldest type of gizzard, the dental folds are narrow and 

 elongated, bearing numerous small teeth, all of equal size, and 

 pointing backwards towards the posterior end. The folds are 



