18 



ARKIV FOR ZOOLOGI. BAND 7. 



NIO 30. 



a liver like that in Balistes this would have been compressed 

 to a dangerous extent. We meet, however, in these forms 

 with a small rounded liver situated entirely on the right 

 side in the body cavity, thus quite out of the pressnre of the 

 air-sac (Fig. 7, Pl. I fig. !.)• In the same forms we find the 

 kidneys as short compact masses in the anterior part of the 



Fig- 7. Body cavity of Spheroides testudineus L. 

 Ventral view. a anus; ais air-sac; i intestihe; I liver; oes opening of 

 oesophagus: p pyloric opening; sfh sphincter between the stomach and 

 the air-sac; st stomach; af anal fin; go goriad; av ventral artery; vi lateral 

 vein; m. hr. 1 muscle of the first branchiostegial radius; vlm vental longi- 

 tudinal muscles; sk skin (cut off). 



body cavity. Whether they are more protected in this some- 

 what altered position from the influence of the air-sac, my 

 observations do not enable me to state. 



The vessels in the skin show generally a winding loop, 

 thus more easily bearing the extension of this, a condition that 

 also must be regarded as a direct adaptation. This fact is 

 shown very distintcly by the lateral veins in Spheroides.^ 



^ See section I of this series. 



