77//: LANCELET. 



VM 



The mouth is oval, surrounded with a circle of cilia 

 tentacles supported by semi-cartilaj 



from a circu moral ring. The mouth leads directly into :i 



large broad pharynx or " branchial sac" (Fig. l v pro- 



ed at the entrance by a number of minute ciliated 1< 



The walls of this sac are perforated by long cil 

 comparable with those of the branchial liana 



and of Balan The wain- which enters the mouth 



- at through these slits where it • - ihe bl 



and enters the peribronchial cavity, thence passing 

 the body through the abdominal pore Fig. L83, p). The 

 pharynx leads to the stomach (/), with which is conni 

 the liver or caecum. There is a pulsatile vessel or tubular 



t / ■ p 



Fio. 183.— a, vent: /. Stomach; a. r^arynx: n. nen-nus cord; p, pore; r, noto- 

 cord; t, tentacles. From Latken's Zoo] 



heart, beginning at the five end of the liver, and ex- 

 tending along the under Bide of the pharynx, sending 

 branches to the sac and the two anterior bran< • • the 

 - il aorta. '-On the dorsal Bide of the pharynx the 

 blood is poured by the two anterior trunks, and by the 

 branchial veins which carry away the aerated blood from 

 the branchial bars, into a great longitudinal trunk 

 dorsal aorta, by which it is distributed throughout the 

 body." (Huxley.) There art' also vessels distributed to 

 the liver, and returning vessels, representing the portal 

 and hepatic veins. The blood-corpuscles are white and 

 nucleated. 



The vertebral column is represented by a notocord 

 which extends to the end of the head far in front of the 

 nervous cord: and also by a Beries of small Bemi-cartilaf 

 ous bodies above thenen - 3ystem, and which are thought 

 to represent either neural spines or tin-ray-. The nervous 

 cord lies over the notoco i; I -not divided into a true 



