126 .Reviews — Prof. Br. Nicholson — British Stromatoporoids. 



Scliluteri, there are large canals in the radial pillars, which send out 

 branches into the connecting processes forming the concentric 

 lamina, and this fact indicates that the fibres of the concentric 

 lamina generally may be hollow. 



One obstacle to ranging the Stromatoporoids with the Coslenterata 

 has been the apparent absence of any tubes for the lodgment of the 

 zooids, but the author has made the important discovery that the 

 skeleton of the typical Stromatoporcz is penetrated by numerous 

 minute, flexuous, but essentially parallel, vertical tubes, which are 

 not bounded by definite walls, but simply inclosed by the vermicu- 

 late fibres of the ccenosteum, precisely like the zooidal tubes in 

 Millepora. Further, these tubes are traversed at intervals by 

 calcareous plates, similar to those of Millepora and tabulate corals. 

 These tabulate zooidal tubes can be clearly distinguished in different 

 species of Stromatopora, and also in such genera as Idiostroma, 

 Winch., and Stachyodes, Barg. Definite tubes are not clearly recog- 

 nizable in the Hydractinioid section of the group, but there are 

 zooidal cavities in Actinostroma, and in Labechia it is probable that 

 the zooids were given off from the surface layer of the ccenosarc. 



The author agrees with Mr. Carter in recognizing the stellate 

 canal system on the surface of the concentric lamina? as the homo- 

 logue of the branching of the ccenosarcal grooves on the surface of 

 the skeleton of many Hydractinia?, and adopts for it Mr. Carter's 

 term Astrorhizas. These canals, though not invariably present, are 

 yet found in so many different forms of the group, that they cannot 

 be accepted as of generic value, and consequently the genus Cceno- 

 stroma, Winchell, in which they are regarded as an essential 

 character, cannot be retained. 



In some anomalous, cylindrical or dendroid, Stromatoporoids, 

 placed in the genera Idiostroma, Amphipora, and Stachyodes, there 

 is a central, axial, tabulated tube, without proper wall, giving off at 

 times lateral branches, which also divide. These " axial tubes " are 

 quite distinct from those of the so-called Caunopora, and the author 

 thinks they may have lodged a stolon or axis of the ccenosarc, and 

 that the smaller lateral tubes may have been occupied by a special 

 series of zooids. 



Certain large-sized lenticular vesicles, resembling the " ampulla? " 

 of the recent Stylasteridw, are present in Amphipora ramosa, Phill. 

 sp., and may probably have lodged the reproductive zooids, and 

 large tabulated vesicles in Idiostroma capitatum, Goldf. sp., may also 

 have served for the same purpose. 



(III.) Systematic Position and Affinities. — The author frankly accepts 

 the views of Carter, Lindstrom, Zittel, and others as to the ccelen- 

 terate affinities of the Stromatoporoids, and regards them as a special 

 group of the Hydrozoa, having relationships on the one hand with 

 Hydractinia, and on the other with Millepora. A detailed com- 

 parison between Hydractinia echinata, Flem., and forms of Actino- 

 stroma, Nich., shows that there is a remarkable similarity between 

 the minute structure of the chitinous skeleton of the former organism 

 and the large calcareous ccenosteum of the latter ; and a similar but 



