34 



noun cement thus in a few words, but it was not so easy to be 

 made. 



After I had satisfied myself as far as I was thus able upon this 

 point, I determined, if possible, to test the correctness of the 

 conclusion. Taking, therefore, a very fine specimen of Membra- 

 nipora pilosa*, in which the processes, exhibiting every character 

 described by Prof. Reid, were well-preserved, I immersed its face 

 in very finely prepared plaster of paris. On removing it after 

 the plaster had hardened, I found, under the microscope, an 

 appearance identical, as to the perforations, with that presented 

 by the casts of the Ventriculidse. 



The reader who may search for these remains of the movcable 

 processes on the Ventriculidse, and, as many will, may not find 

 them, and who may therefore too hastily doubt the accuracy of 

 my observations, will do well to refer to p. 332-3 of Johnston's 

 ' Zoophytes/ where he will find that, in even recent specimens, 

 " they are not present in every specimen of any of these species, 

 and indeed are very rarely to be seen on some of them, and when 

 present it is only upon some of the cells." If this is the case in 

 recent specimens how much more is it to be expected in fossil 

 specimens that the traces of the former existence of these pro- 

 cesses will be sometimes few, sometimes altogether absent ! The 

 universal friableness of the chalk and the general solidification 

 of the flint often almost or totally obscure them. Doubtless, 

 moreover, the originals of many of the specimens which remain 

 both in chalk and flint were dead when enveloped, for the views 

 already stated require only that the soft parts should have been 

 yet undecomposed, not that the animal should have been alive. 



I am enabled, by some specimens in an extraordinary state of 

 preservation with which frequent personal excursions into the 

 field have rewarded my careful search, to add some description of 

 these processes as existing in the living Ventriculidse and derived 

 from other observation than that of mere casts only. When the. 

 places of all are preserved, which is very rarely the case, they are 

 disposed not without some regularity: it would appear that one was 

 appropriated to each polyp, whose celFs mouth it doubtless swept 

 in the living state as the mouths of the polyp-cells of the Cellu- 

 laria described by Prof. Reid are swept by the processes existing 

 in those species. As in those cases, the process was affixed to a 

 slight projection of the polypidom on the outer edge of each 

 polyp-cell. As in those cases also the processes tapered off gra- 

 dually to a point in the Ventriculida3, though the base of the 



* In this specimen there are all the parts described by Prof. Reid as ap- 

 purtenant to these processes, though Dr. Johnston does not describe the spe- 

 cies as exhibiting them. 



