22 ARKIV FÖR ZOOLOGI. BAND 7. NIO 30. 



Explanation of Plates, 

 Plate I. 



Fig. 1. — Spheroides festudineus L. (Lengtli 18 mm.) Trans- 



verse section through the body in tlie region of the stomach. v. 



Gieson"s mixture. 



-f stomacli 



+ + air-sac 



ai-bl air-bladder 



ao aorta 



h. c. body cavity 



hl. v. blood-vessel 



cor. corium 



c. t. subcutaneous connective tissue uniting the air-sac with the ven- 

 tral body wall. Immediately interiorly to the corium there is a 

 thin layer of transverse muscles and interiorly to this a layer of 

 longitudinal ones, most distinct below the air-sac. 



ep. epithel of skin 



g. c. gill cavity 



Jc. kidney 



1. liver 



sjjh sphincter between the air-sac and the stomach. 



Fig. 2. — Spheroides testudmeus L. (Length 18 mm.) Trans- 

 verse section through the body in the region of the oesophagus. — 

 Boraxcarmin, Bismarckbrown, Indigcarmin. 

 1. m. part of longitudinal muscles attaching at the ligament between 



the ventral ends of the pectoral arch. 

 oes. oesophagus. 



Other reference letters as in Fig. 1. 



Plate II. 



Fig. 1. — Spheroides testudineus L. Yertical section through 

 anterior part of body. 

 + stomach; ++ air-sac; "^^pyloric opening. 



Between the stomach and air-sac there is a fold containing a sphincter 

 muscle. The air-sac is by subcutaneous connective tissue united with 



