50 



sucli a form in Cauda arachnoides (Lamouroux Encyclop, 

 Methodique 5, p. 64, figs. 18 to 22), where the branches are 

 connected with tubular fibres, but these are flexible, horny, 

 and not calcareous. There is, however, a species of Hornera, 

 R. GamUerensis, Busk, in the polyzoan limestone of Mount 

 Gambier, a middle cainozoic tertiary fossil, where the ligulate 

 celluliferous portions are united bv transverse calcareous bars. 

 The analogy of this fossil to Fenestella is very great. In 

 Hornera, however, the back of the cells shows concentric ridges 

 of growth, whereas that of Fenestella is fibrous. The casts of 

 the two forms are the same, and widely as they are separated 

 in point of time, I am much inclined to the opinion that 

 Hornera Gamhierensis is one of the recent analogues of the 

 Devonian Fenestellae. 



Were these fossils entirely calcareous ? In answer to this 

 it must be remembered that a corneous substance, the nature 

 of which has not received the attention it deserves, forms the 

 root byssus or point of attachment of many polyzoa. It also 

 forms the point of attachment between each cell in Catenicella, 

 and the junction of the internodes, in Calpidium, Salicornaria, 

 &c. I have reason to believe that it lines the cells in 

 all polyzoa. Something like that is seen in Catenicella 

 under the microscope. In examining many hundred specimens 

 I remarked that similar species showed the same optical 

 peculiarities under the polariscope. In Catenicellse these were 

 generally slight ; in Bugula on the other hand most brilliant. 

 (Sometimes when the whole calcareous portions of Fenestella 

 are removed, there remains a series of rounded cells, which 

 are not effected by acids. These may be the corneous lining 

 of the cells. It would seem from the fact that a calcareous 

 root is never seen in Fenestella, that it had a fibrous byssus 

 like Cauda, &c. How these bars and extra cellular portions 

 are formed is not known, even in existing species. The body 

 contained in the cell must not, however, be considered as an 

 individual. Indeed, in living species when thousands of 

 the cells are open one of them is touched, the whole draw 

 back, and close instantly. We must consider the polyzoarium 

 like a plant with leaves, bark, buds, flowe'rs, seeds, and the 

 different processes belonging to each. These constitute one 

 whole which they subserve by different functions endlessly 

 repeated in one individual. 



Finally the fewness of species of one genus, though indi- 

 viduals are as common as in any deposit is a remarkable fact. 

 In recent rocks genera of polyzoa can be counted by tens, and 

 species by hundreds. It must, however, be remembered that 

 the past forms are as highly organised as those of the present 

 day, and belonging to specially developed classes. 



