90 AKT. 4. — N. YATSU : 



specimen which I was able to observe, the remnants of the 

 muscles were still visible attached to the occlasor anterior as 

 shown in Fig. 86 (PL VI., m. vL). 



Peduncle. — After the peduncle becomes protruded from the 

 posterior mantle cavity it undergoes a noteworthy change. Its 

 epithelium seems to react to the new stimuli and commences to 

 secrete a superficial gelatinous layer (PI. VI., Fig. 87, and PI. 

 VIII., Fig. 123). This secretion seems to be at first very viscous 

 and soft, but hardens by degrees. The power of secretion is 

 evidently greatest at the end of the peduncle, where the epi- 

 thelial cells are of a higher collumnar shape and here the 

 gelatinous layer is naturally thickest (PI. VIII., Fig. 123). In 

 longitudinal sections radiating lines are seen in the gelatinous 

 layer at the tip of the peduncle (PI. VI IL, Fig. 137) as Ekmann 

 ('96) has observed in the adult. The mass between these radiat- 

 ing lines appears to correspond to the product of secretion from 

 one cell of the peduncular epithelium. On this point Blochmann 

 ('00) is of the same view as myself (p. 104). It may be added 

 that these radiating lines are not seen in transverse sections of 

 the adult peduncle. This fact indicates that the mass secreted 

 from each cell is fused to form a ring. 



Chemically the gelatinous secretion is quite différent from 

 the shell. Treated first with borax carmine and afterwards with 

 picric acid as a counter stain, the shell takes a yellow color, 

 while the secretion stains red as in the case of cytoplasm. This 

 reaction toward stains persists in the adult. Kruckenberg ('85) 

 studying the adult Lingula, says : " die elastische Hülle des 

 fleischigen Stieles besteht fast ganz aus ihn [chitin]," (p. 413). 

 As to the chemical composition of the shell the above author and 



