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EDWARD L. RICE. 



like that separating off the interlamellar connection in the other 

 filaments. The appearance was rather that of a thinner spot or 

 constriction preliminary to complete perforation. Study of the 

 sections fully confirmed this interpretation. In Fig. 9 three such 

 sections are represented, their positions being represented by light 

 horizontal lines in Fig. 8, D. The section nearest the tip (Fig. 

 9, A) shows a direct connection between the cavities of the two 



Fig. 9. Transverse sections of filament represented in Fig. 8, D. Position of 

 sections shown by horizontal lines in Fig. 8, D, marked with corresponding letters. 

 Magnification 540. 



filament limbs in the neighborhood of the edge of the gill. Cor- 

 responding sections of other filaments show the same arrangement. 

 The section farthest from the tip (Fig. 9, C) shows an essentially 

 similar arrangement, which is duplicated by sections through the 

 interlamellar connections of the other filaments. In the inter- 

 mediate section (Fig. 9, B) the gill filament is strongly constricted, 

 and the connection of the cavities of the two limbs is entirely 

 interrupted. The next stage would be a complete perforation in 

 place of this constriction, and the local separation of the filament 

 limbs. Three successive degrees of such separation are shown 

 in Figs. 8, C ; 8, A ; and 8, E. 



