TAHITI. 



531 



gastropore, just as in the Tahitian Millepora (see Fig. 2). In 

 other parts of the same specimen, a further complication arises, 



DIAGRAMS ILLUSTRATING THE SUCCESSIVE STAGES IN THE DEVELOPMENT OF THE CTCLOSTSTEMS 



OF THE STYLASTERIDiE. 



1 In Sporadopora dichtoma. 2, 3 Allopora nobilis. 4 AUopora profunda. 5 AUopora miniacea. 

 6 Astylus subviridis. 7 Distichopora coccinea. s Style ; dp dactylopore ; gp gastropore ; d in 

 fig. 6, inner horseshoe-shaped mouth of gastropore. 



as shown in Fig. 3. A shallow groove leads from each of the 

 dactylopores to join the gastropore cavity, and a radiate figure is 

 produced. No doubt the grooves are developed by the constant 

 bendino- inwards of the tentacular zooids to feed the mouth- 

 bearing zooid in the gastropore. 



A more complete development of radiate systems occurs in 

 another species of Allopora (A. profunda), as shown in Fig. 4. 

 Here 12 dactopores surround each gastropore, and the grooves 

 are much deepened. The dactopores in this case have small 

 rudimentary styles, which structures are usually confined to 

 the gastropores. In Allopora mineacea (Fig. 5), the styles in the 

 dactopores are large, and have brush-like tips like the styles of 

 the gastropores. 



In the genus Astylus, neither kind of pore has a style, the 

 radiate arrangement is most complete, and the highest condition 

 of development of the circular systems of zooids (c'yclosy stems) 



M M 2 



