304 Mr. H. J. Carter on the Stromatoporidae. 



each side supersedes the five or six small sharp spines of that 

 species. The edges of the terminal spine are serrated. 



Astacus IceviusculuSj Dana. ' 

 Columbia River, Puget Sound. 

 San Francisco, Aug. 28, 1878. 



XXXVI. — Oft the probable Nature of the Animal which pro- 

 duced the Stromatoporidae, traced through Hydractinia, Mil- 

 lepora alcicornis, and Caunopora, to Stromatopora. By H. 

 J. Caeter, F.R.S. &c. 



As there are undoubtedly several species of Stromatopora^ and 

 each species may have several varieties, while the whole may 

 be variously altered by mineralization, these contingencies 

 are too numerous for me to undertake the palasontology of the 

 whole group, and therefore I shall confine myself solely to the 

 probable nature of the animal which produced them. 



I need hardly premise that in proportion to the knowledge 

 of beings actually living will be that of those which have 

 passed away — that is, that it is impossible to be a good palse- 

 ontologist without being a good morphologist, either specially 

 or generally, and therefore that a knowledge of geology alone 

 cannot make a good palaeontologist. 



Take, for instance, the following fact, which no amount of 

 fossil material could afford, and which nothing but a know- 

 ledge of recent structure could supply, and the foregoing 

 premise becomes evident. 



Thus, the embryo of Hydractinia echinata begins its struc- 

 ture, both soft and hard, by developing a sarcodic membrane 

 which is traversed by a vascularity consisting of rami^ ramu- 

 scidi, ramuscunculi, &c., over which minute points of chitinous 

 or horny matter subsequently appear along the course of the 

 vessels (that is, outside their walls), which, after having grown 

 into branched elements, ultimately become incorporated in the 

 formation of the fibre of the polypary or coenenchyma, after the 

 manner of Millepora alcicornis^ as will be more particularly 

 explained by-and-by (' Annals,' 1873, vol. xi., and 1877, 

 vol. xix.). When the soft parts are abstracted the sjpaces alone 

 which they occupied are left, whereby thecoenenchyma becomes, 

 as it were, the mould of the vessels. Fari passu with the 

 development of the coenenchyma is that of the polypites and 

 the development of new vascular ^/oce, from which it happens 



