SECTION THROUGH ATRIAL PORE. 



207 



D. Transverse Section passing through the Atrial Pore. 



1. General characters. The section is smaller than the pre- 

 ceding one, and the myotomes reach much further 

 down the sides. The intestine is cut across, but the 



Fig, 



43. — Amphiozaa lanceolatus. Transverse section oi an adult 

 specimen, passing through the atrial pore. The boundary of the 

 atrial cavity is indicated by a thick black line. (a. m. m.) 



A, skeleton of dorsal fin. B, spinal cord. C, notochord, D, connective- 

 tissue sheafcli of notochord. H, atrial cavity. K, intestine. O, coelomic 

 space surrounding intestine. P, metapleural canal. Q, dorsal aorta. XT, 

 portal veins. V, atrial pore, represented diagrammatically. w, metapleural 

 folds. 



section lies entirely behind the reproductive organs. 

 The metapleural folds are present, but are' much 

 smaller than in sections B and C, and between them 

 in the median plane is the atrial pore. 



The skin, and the skeletal, muscular, and nervous 



