40 PROCEEDINGS OP THE ACADEMY OF [1886. 



water-channels are not a part of the organism, and prove on 

 accurate examination to be either accidental perforations of the 

 skeleton by boring animals, or else, are the stems of certain corals, 

 particularly of Syringopora^ which have grown up simultaneously 

 with the Slromatopora, parasitically enveloping them. 



At the time I wrote the before-mentioned manuscript I also 

 believed a close affinity existed between the sponges and Stro- 

 matopora, but since Carter and others have pointed out the simi- 

 larity existing between the calcareous skeleton of Hydractinia 

 and Stromatopora I am convinced that the similarity between the 

 calcispongiae and Stromatopora is merely an external one. The 

 mode of gi'owth and organization of the sponges essentially differs 

 from that of Stromatopora. The sponges are through their entire 

 mass permeated by a system of channels systematically arranged 

 so as to make it evident that all parts of the sponge are destined 

 to perform simultaneously a vital function in the compound organ- 

 ism. There is nothing in their structure which could with pro- 

 priety be compared with the uniform periodicitj^ in the growth of 

 a Stromatopora, which forms layer after la3'er in endless succes- 

 sion, one being the exact analogue of the other. The layers in 

 many instances are almost entirely shut off from communication 

 with the subjacent portion of the laminated skeleton. We have 

 to infer, therefore, that the live portion of a Stromatopora was 

 confined to the uppermost superficial strata, while the iuterlaminar 

 cell-spaces towards the interior gradually were abandoned and 

 became dead portions of the skeleton, as is the case with the skel- 

 etons of Hydractinia, and generally with all true corals produc- 

 ing a calcareous ston}' skeleton. 



In a second chapter the authors give the characteristics of 

 Stromatopora, considering as type of the genus the Goldfussian 

 species Str. concentrica and polymorpha, both found in the Eifel, 

 Germany. 



Their description reads : " Stromatopora is composed of a suc- 

 cession of thin, close-set laminae, arranged concentrically round 

 one or more imaginary centres. These concentric fundamentally 

 horizontal laminae are separated by interspaces, which are crossed 

 by more or less numerous vertical pillars ; hence tlie vertical sec- 

 tion of a Stromatopora exhibits a number of approximately hori- 

 zontal layers and intervening spaces, the latter divided by upright 

 pillars into a number of vesicular compartments. The entire lami- 



