THE ANTHOZOA 



31 



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 KoUiker, 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, Kdll., from the prorachidial aspect. 

 2. — Kophobelemnon Burgeri, Herklots ; iiietanichidial aspect. 

 3. — Stachyptilum Macleari, KiJll. ; luetarachidial aspect. 

 4. — Umbeliula Carpenteri, Koll. ; Tiietarachidial aspect. 

 5. — I'ennatula phosphorea, Linn. ; nietarachidial aspect. 



0. — Section of the racliis of t'lnnatxda phoaphorca bearing a single pinna, a, axis ; h, nieta- 

 -nchidial ; c, prorachidial ; f/(^ jjararachidial stem canals ; sp, siphonozooids ; 2, autozooids. 



7. — Jlenilla reniformis, Pallas. (1 to 4 after Kcilliker, 5 to 7 original.) In all the figures. 

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



Kolliker, are the pararachidcs. 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 tlie rachi.s, and an abaxial. 



