312 



MANUAL OF ZOOLOGY 



SECT. 



On the dorsal surface of the anterior part of the trunk is a double 

 row of small slits the gill-slits (Fig. 195, br^) each row situated in 

 a longitudinal furrow; these slits increase in number throughout. The 



div 



prob. ske-l 



dors.v 



FIG. 196. BalanoglOSSUS. Diagrammatic sagittal section of anterior end. card, 

 s, cardiac sac; div, diverticulum (supposed notochord) ; dors, n, dorsal nerve 

 strand; dors, sin, dorsal sinus; dors, v, dorsal vessel; mo, mouth; prob, pro- 

 boscis; prob. po, proboscis pore; prob. skel, proboscis skeleton; vent, n, ven- 

 tral nerve strand; vent, v, ventral vessel. (After Spengel.) 



ccelom of the trunk is divided into two lateral closed cavities by a verti- 

 cal partition (dorsal and ventral mesenteries). 



The mouth (Fig. 196, ;0,) is situated ventrally at the base of the 

 proboscis, within the collar. Into the dorsal half of the anterior portion 



