TYPE ANNELIDA. 



229 



which each ring of the middle region of the body bears an 

 appendage which functions as a gill. In another marine form, 

 Pontobdella, large warts occur on certain rings, which prob- 



FiG. 106.— Antbkior and Pos- 

 terior Extremities of Ma- 

 crobdella sesteriia (after Whitman). 

 an = auus. 



fo = opening of oviduct. 

 ge = copulatory glands. 

 mo = opening of vasa deferentia 

 oc = eyes. 



p = nepliiidial pores. 

 sp = sense-papilla. 



1-100 = annuli. 



i-xxv = melameres. 



OV.ji ys 



Fig. 107. — Diagrams to show Ar- 

 rangement OF Blood-sinuses of (A) 

 Hirudo, (B) Glepsine, and (C) NephelU 

 (after Bourne). 



al = digestive tract, 

 c = coelom. 

 ds = dorsal sinus. 

 Is and li) = lateral sinus or vessel. 

 n and nc = ventral uerve-cord. 

 ne = nephridium. 

 on = ovary. 

 U = testis. 

 m = ventral sinus. 



ably are mainly respiratory in function, being richly supplied 

 with blood-vessels. 



The exterior of the body is covered by a cuticle, beneath 

 which lies the hypodermis. The muscular tissue which un- 

 derlies the hypodermis consists, as in other Annelida, of layers 



