REPRODUCTIVE PROCESS. 



G3 



will as from their only occasional development, it seems a not unreasonable con- 

 jecture that these " marginal vesicles" gave lodgment to the reproductive zooids, 

 and that they are, therefore, of the nature of " ampullae." 



In the Devonian Rocks of Devonshire, and also, more abundantly, in the same 

 deposits in the Paffrath district, I have found a Stromatoporoid, which I think to 

 be probably identical with the Stromatopora (Tragos) capitataoi Goldfuss. As the 

 ccenosteum of this form is traversed by irregular tabulate tubes of a much larger 

 size than the ordinary zooidal tubes, it should probably be referred to the genus 

 Idiostroma, Winch., and should stand as /. capitatum, Goldf., sp. Scattered 

 through the tissues in this species, in a large number of specimens, are vesicles 



Fig. 8. 



Fig. 8. — A. Vertical section of Idiostroma capitatum, Goldf. (?), from the Devonian Eocks of Hebborn 

 (Paffrath district), enlarged twelve times; u. Tangential section, similarly enlarged; a a. Supposed 

 " ampullae ;" c c. Large tabulate tubes ; t t. The ordinary zooidal tubes. 



(Fig. 8) of a lenticular, oval, spherical, or elongated shape, which are bounded 

 principally by the general skeletal tissue, and commonly have no proper wall of 

 their own. These are mostly about 1 mm. in diameter, less or more; and they 

 are occasionally crossed by one or more calcareous partitions or tabulae. Some- 

 times they appear to be appended to the sides of the large tabulate canals which 

 traverse the skeleton in this type ; but at other times they seem to have no con- 

 nection with these. They occur, as might be expected, at all depths below the 

 surface, since the species is one which grows by the formation of successively 

 superimposed laminae, and each successive layer constitutes therefore in its turn 

 the actual surface. 



I have not recognised these curious structures with any certainty, or in any 

 conspicuous form, in any other Stromatoporoid except the one just mentioned ; 

 but it is quite possible that they will be found in others if carefully looked for. 

 In the particular type above alluded to, thin sections prove conclusively that these 

 vesicles are really parts of the organism in which they are found, and are not 



