IV 



COELOME 



201 



In the Am- 

 phibia and Aniiii- 

 ota the pericardiac 

 cavity becomes 

 telescoped back A. 

 into the general 

 peritoneal cavity, 

 its hinder Wall be- 

 coming extended 

 so -as to form a 

 thin membranous 

 bag enclosing the 

 heart and separat- 

 ing it from the 

 other viscera. 



Apart from the 

 walling off of the 

 pericardiac from 

 the main periton- 

 eal cavity there is 

 found in the case 

 of the Amniota a 

 well-marked tend- 

 ency for the latter 

 cavity to undergo 

 further subdivi- 

 sion, special por- 

 tions becoming 

 more or less com- 

 pletely walled in 

 by secondary fu- 

 sions taking place 

 between apposed 

 portions of the 

 peritoneal lining. 



FIG. 110. Differentia- 

 tion of the ruyotome 

 as seen in transverse 

 sections of Lepidosircn 

 larvae. 



A, st age 30 ;B, stage 31 + ; 

 0, sta-r 83; I), stage 35-; 



E, dividing ntyoblasts of 

 iniM-r wall from stage 3<>. 

 'ii>>', niyoblasts () f imirr 

 wall: />/'. inyohlasts of 

 "ut.T wall ; ,nf, contractile 

 tihrils; cm:, vacimlc. The 

 contractile fibrils cut across 

 an- shov. n as distinct black 

 lots. 



772 1 



vac. 



B. 



