THE ANTHOZOA 



and ventral leads to confusion, and to avoid ambiguity the following 

 terms will be applied to the several regions into which the rachis of the 

 bilaterally symmetrical Pennatulacea may be divided : The face of the 

 rachis which is sterile and coincides with the asulcar aspect of the 

 terminal zooid, i.e. with the ventral surface of Kolliker, will be called 

 the prorachis. The opposite face, equivalent to Kolliker's dorsal surface, 

 is the metarachis. The two remaining faces, the lateral surfaces of 



FIG. XVI. 



1. Virgularia Bromleyi, Roll., from the prorachidial aspect. 



2. Kophobelemnon Burgeri, Herklots ; metarachidial aspect. 



3. Stachyptilum Macleari, K611. ; metarachidial aspect. 



4. Umbellula Carpenteri, Koll. ; metarachidial aspect. 



5. Pennatida phosphorea, Linn. ; metarachidial aspect. 



6. Section of the rachis of Pennatula phosphorea bearing a single pinna, a, axis ; 6, meta- 

 rachidial ; c, prorachidial ; dd, pararachidial stem canals ; sp, siphonozooids ; 2, autozooids. 



7. Renilla, reniformis, Pallas. (1 to 4 after Kolliker, 5 to 7 original.) In all the figures. 

 R, rachis ; P, peduncle ; sp, siphonozooids ; z, zooids. 



Kolliker, are the pararachides. Milnes Marshall (77) has shown that the 

 symmetry of the lateral, or as we may now call them, pararachidial zooids, 

 bears a definite relation to the symmetry of the colony. The asulcar 

 aspect of each zooid is turned towards the stem, and therefore may be 

 called axial, the sulcar aspect is turned away from the stem and is 

 therefore abaxial. When, as is the case in Pennatula and Pteroeides, 

 several elongated zooids are fused together side by side to form leaflets or 

 pinnae, these are always situate on the pararachides and are inserted 

 diagonally on those surfaces. Hence in each leaflet two surfaces may be 

 distinguished an axial, turned towards the rachis, and an abaxial, 



