136 On the Growth and Variability of Madreporaria. [Apr. 12, 



had they been assumed to have come from different localities, new species 

 would have been made of them. 



Several specimens are very costulate, and there are crests to all the 

 larger costse; in some there are wart-like growths in those situations, and 

 in these forms the calice is sometimes widely open, or very compressed, 

 or normally slightly so at its orifice. 



In at least one fourth of the specimens the shape of the corallum, in- 

 stead of being subturbinate and compressed above the round pedicel, is 

 tall and cylindrical ; and there are no costal ridges of any importance. 

 Moreover the size of the calices and septa varies in this series. 



Some specimens, otherwise normal, have very broad basal expansions 

 out of all proportion with the height. But the most interesting variation 

 is noticed in those specimens which have widely open calices and exsert 

 septa ; for, added to these specific structures, are costal crests, ridges, pro- 

 cesses, and root-like projections coming from the body, peduncle, and base. 

 These projections are either free at their end or are attached to some sup- 

 port ; sometimes the growths are in relation to the costal line, and in others 

 they cannot be maintained to be so, and they are either smooth, granular, or 

 like shagreen. There is no epitheca on the coral, and the root-like projec- 

 tions are therefore growths of the ectoderm. Some act as supports ; but 

 most have been produced by the irritation of an Annelid, which, after boring 

 out of the cable came in contact with the coral, which endeavoured more 

 or less successfully to cover it up. 



Those processes which are beyond the reach of Annelids and which act 

 as supports singularly resemble those root-like growths which are of 

 generic or specific importance in many groups of Madreporaria. 



Flahellum, Rhizotrochus, Rhizophyllum, Omphyma, &c. are genera which 

 possess such root-forming species. But the root-like processes of Flahellum 

 have a higher physiological interest than those of Desmopliyllum ; for some 

 finally separate the base of the coral from its attachment by their down- 

 ward growth-pressure; nevertheless the development of root-processes by 

 the cable covering Desmophylla is suggestive and important, although some 

 are morbid growths. 



The cylindroid specimens would most probably be considered speci- 

 fically distinct from the others were they found away from them or in 

 strata. They are very suggestive ; for in palaeontology the shape of the 

 corallum, the contour of the calice, and the relative size of the septa are 

 often considered to establish species ; and such genera as Trochocyathus, Tro- 

 chosmilia, and Montlivaltia amongst Mesozoic corals, and CyathopJiyllia 

 and Zaphrentis amongst the Rugosa, teem with specific names which are 

 not established on better grounds than that of the cylindroid Desmo- 

 johyllum. 



The Lophohelim on the cable present great bud variation; and the 

 young and old corallites are of many different shapes, from the turbinate 

 to the tubular. But che most important structural peculiarities are of two 



