[//. S. Cheavin, F.RM.S. 



An Air-tube Junxtion. 



^iA'!fhL^?rn!n".oL'I^=,-'?P'^f °T-"''''™ °^ the silkwonn, magnified about eight v times, to show the spiral thread which in hfc prevents the 

 air-tubes trom coUapsuig under the pressure of the other organs. 



141 



