A portion of the cylindrical wall of {HEAD ~ the receptacle} is provided with {TAIL ~ classifying openings}, for example by providing a screened opening as a band around the receptacle 
A portion of the cylindrical wall of { HEAD ~ the receptacle } is provided with { TAIL ~ classifying openings } , for example by providing a screened opening as a band around the receptacle
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH