328 Animal Biology 



— /ncurrent siphon 

 - — txcurrent siphon 



Mantle 



Tunic 



Qonqlion 



AncJ5 



^ Genital duct 



Testis 



•%\ — Ovar-y 



— Digestive glands 



— Isophagus 

 --Intestine 



— -Stowach 

 — Branchial fold 



- - tndostyle 



- - yttrium 



- - Pharynx 



Fig. 141. — A typical ascidian or sea squirt (Molgula manhattensis) of the sub- 

 phylum Urochordata (Tunicata) . The diagram is from the left side of the body. 

 The courses of water and food through the body are shown by arrows. (From 

 Potter: Textbook of Zoology, The C. V. Mosby Co.) 



Fig. 142. — Amphioxus, a simple chordate, subphylum Cephalochordata (general 

 structure of a lateral view), nc, Notochord; s.c, spinal cord (nervous); my, 

 myotomes (muscle segments); r, fin rays; d.f-, dorsal fin; c.f-, caudal fin; cir, 

 cirri on edge of vestibule leading to the mouth; m, mouth surrounded by a fringed 

 velum; g, gills (branchiae) constructed of alternate slits for the passage of water 

 and supporting plates in the walls of which are blood vessels; o, ovaries; /, liv^er; 

 a. p., atrial pore; in, intestine from which the liver arises as a pouchlike diverticu- 

 lum; v.f., ventral fin; a, anus. (From Galloway: Textbook of Zoology. Copy- 

 right P. Blakiston's Son & Co., Inc., publishers.) 



"FiJ^v 



:?? 



">■• 



^. 



^ 



NostrW 





Pharyngeal clefts Mouth 



Fig. 143. — A lamprey of the class Cyclostomata, phylum Chordata. Note the 

 circular, sucking mouth, the median unpaired nostril, the seven pharyngeal clefts 

 ("gill slits"). Lampreys frequently attack fishes, causing their death. 



