The porifera and coelentera . )roso])ijles. Similarly, the wide openingby which the current passes out of the chamber may be termed theapopijle. The follo^ving parts can, therefore, now be distinguished in thefully developed canal system of the second type (Fig. 44, B). The A Ij osc. \\ f^P flc. Mc. 4 ^ flc \ost. B Fic!. 44. Diagrams of the second tyi)o of canal systpm. A, simple type, with separate radial , more complex type, with radial tubes fused and thickened distally to form cortex and in-current canals ; a portion only of the wall is represented, o^l, ostia ; ,
The porifera and coelentera . )roso])ijles. Similarly, the wide openingby which the current passes out of the chamber may be termed theapopijle. The follo^ving parts can, therefore, now be distinguished in thefully developed canal system of the second type (Fig. 44, B). The A Ij osc. \\ f^P flc. Mc. 4 ^ flc \ost. B Fic!. 44. Diagrams of the second tyi)o of canal systpm. A, simple type, with separate radial , more complex type, with radial tubes fused and thickened distally to form cortex and in-current canals ; a portion only of the wall is represented, o^l, ostia ; , incurrent canals ;, prosopyle ; /?.<?, tiagellated chamber ; ), apopyle. Other letters as in last. water enters through the ostia (dermal pores) into the incurrentcanals ; thence it passes through the prosopyles (chamber pores)into the ciliated chambers; and from them it passes by the wideapopyles into the gastral cavity and out through the osculum. Thegastral layer, being restricted to the chambers, is discontinuous, asit is in all types of canal system above the first type. Third Tifpe of Canal System.—The third type can be derived fromthe second by a further process of folding of the body wall, givingrise to bays or diverticula of the gastral cavity, into each of whichseveral chambers open tog
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