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Notes on the Respiratory Mechanism of Corystes 



Cassivelaunus. 



By 

 Kathleen E. Zimmermann, B.Sc, 



University College of Wales, Aherystunjth. 

 With Plate V. 



I. INTEODUCTIOK 



In his paper in the Journal of the Marine Biological Association for 

 August, 1896, Garstang treated of some structural peculiarities of 

 Corystes cassivclauiuis in relation to their biological significance. A 

 brief summary of his observations on the respiratory mechanism may 

 be given as follows : In Corystes cassivelaunus the second antennae 

 are greatly elongated and are fringed by a ventral and a dorsal row 

 of hairs. The opposing rows of hairs interlock, with the resulting 

 formation of a median " antennal tube." The double row of hairs is 

 continued back along the three basal joints of the antennae, which joints 

 are bent at right angles to one another ; these hairs, projecting towards 

 the median line, together with a median tuft of hairs springing from 

 the rostrum, form the hairy roof of the proximal part of the antennal 

 tube. The antennal tube opens posteriorly into a median " prostomial 

 chamber," which in turn leads by a wide aperture to the branchial 

 cavity of each side. The prostomial chamber is roofed by the rostrum, 

 the antennal and epistomial sternites, and the prelabial plate. Its 

 floor is imperfect, and is formed by the anterior part of the third 

 maxillipeds behind and in front by a quadrangular sieve of hairs 

 springing from the two basal joints of the second antennal, the anterior 

 pterygostomial processes, and a special anterior process of the fourth 

 joint of the external maxillipeds. 



The habit of Corystes is to burrow beneath the sand, where it 

 remains concealed, with only the tip of the antennal tube projecting 

 above the sand surface. A current of water (the respiratory current) 

 is sucked down through the antennal tube, and passes backwards into 

 the prostomial chamber, where it divides into right and left streams, 

 which pass into the right and left branchial chambers. The stream 

 eventually emerges from the branchial chamber along the whole extent 

 of the edge of the branchiostegite. 



