138 



I'RJNCII'LES OF ANIMAL BIOLOGY 



of the clavicle. A cavity, the glenoid fossa, located at the junction of 

 scapula and coracoid serves as the point of attachment of the fore-limb. 



p. cor 



-UL 



'="'::^orr- 



n m 





ph 



Urn. 



Fig. 107. — Diagrams of generalized fore (A) and hind (B) limbs with limb girdles. 

 actb, acetabulum; CL, clavicle; en. 1, en. 2, centralia; COR, coracoid; dst. 1-5, distal row 

 of carpals and tarsals; FE, femur; FI, fibula; fi, fibulare; gl, glenoid fossa; I-V, digits; 

 IL, ilium; int, intermedium; IS, ischium; mtcp. 1-5, metacarpals; mtts. 1-5, metatarsals; 

 ph, phalanges; p.eor, precoracoid; PU, pubis; RA, radius; ra, radiale; SCP, scapula; TI, 

 tibia; li, tibiale; UL, ulna; ul, ulnare. (From Parker and HasweU's Textbook of Zoology.) 



A B 



FiQ. 108. — Nervous mechanism of Hydra. A, neuromuscular cell from ectoderm; 

 B, ectodermal nerve plexus. The long fibrils in the background are the contractile parts 

 of neuromuscular cells. They lie in the mesoglcea. (From Schneider.) 



Each side of the pelvic girdle consists of an ilium., ischium and pubis. 

 These three bones in a generalized skeleton are arranged similarly to the 

 bones of the pectoral girdle. The cavity at the junction of the three 



