PLATE XXI. 



M.EAXPRIXA LABYRLNTHICA (Ellis & Solander). 



Fig. 141. — Transverse section through the stomodaeal region of part of a colony, including four stomodsea and their 

 associated mesenteries. The number of mesenteries inserted on each stomodieum is variable, and in 

 the portion represented no incomplete pairs occur. The septal invaginations at this level are mainly 

 entoccelic. The line of separation between each stomodaeal system passes through two entocoeles, never 



through an exoccele. No pairs of directives ever occur. The endoderm is not represented. ;< 40. 



Fig. 142. — Transverse section at a still lower level, showing how the polypal cavity is encroached upon by the 

 ingrowth of the entosepta and their fusion in the middle. In some cases the interseptal loculi thus 

 produced are wholly distinct in section, but elsewhere several are in communication. The two 

 mesenteries included within each loculus belong to adjacent pairs, no exosepta being present. X 110. 



Fio. 143.— Section through a mesenterial filament and the swollen part of the mesenterial endoderm immediately 

 behind. X 320. 



FlG. 144. — Section through another filament, in which many of the cells on the left side are tilled with granular 

 contents. X '■'>-"■ 



Fig. 145. — Section through a part of a mesenterial lilament in which the cells have all become enlarged and 

 glandular, the modification having also affected the swollen endoderm behind (see p. 47:'>). Three 

 granular gland cells are found in the section, in addition to the clear gland cells. X 400. 



Fig. 146. — Section through a mesentery containing two ova. X 300. 

 040 



