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HANDBOOK OF INVERTEBRATE ZOOLOGY. 



striated plate suspended in the mantle cavity by its upper 

 margin, and terminating below in a continuous free edge. 

 When the gills are roughly handled in a living specimen, 

 or one which has died in pure water, or in many alcoholic 

 specimens, the lower edge of the lamella will be found to 

 fray out, or break up into a great number of fine threads, 

 and the gill now resembles a fringe rather than a flat plate. 

 In the uninjured living animal these threads will soon be 

 found to rearrange themselves in a continuous lamella, 

 somewhat in the same way that the 

 plumes of a ruflied feather soon 

 reassume their natural positions. 



Fig. 150. — Diagram of the gills on one 

 side of the body of Mytilus edulis, magnified 

 about eight diameters. (Drawn from nature 

 by W. K. Brooks. ) 



a. Outer lamella of outer gill. h. Inner 

 lamella of outer gill. c. Outer lamella of inner 

 gill. d. Inner lamella of inner gill. e. Inter- 

 lamellar junctions. /. Cavity of tentacle, 

 shown only on the left side. h. Inter-ten- 

 tacular junctions, i. Line of attachment of 

 gills to body, k, k'. Blood channels. 



Fig. 150. 



1. In an alcoholic specimen note that the threads or gill 

 tentacles which compose the outer gill are attached to the 

 body in such a way that their proximal portions make up 

 the inner lamella of the outer gill. 



2. At the bottom or free edge of the gill each tentacle 

 bends outwards and upwards upon itself, so that its distal 

 half lies parallel to and near its proximal half. The dis- 

 tal portions of the tentacles make up the outer lamella of 

 the outer gill. 



3. The gill tentacles of the inner gill are bent upon each 



