process was rather proportionally broader in the latter than in 

 the former. 



Any special peculiarities in these processes exhibited by any 

 species will be noticed in the descriptions hereafter to be given 

 of each separate species. 



The discovery of these moveable processes was certainly an im- 

 portant and very interesting point in the anatomy, as it was an 

 essential aid towards determining the proper position and true 

 affinities, of the animal to which they belonged. It will be ob- 

 served that these processes are affixed to the strict polypidom, not 

 to any distinct and separable external cell, thus adding another 

 to the many evidences afforded by the Ventriculidse that the 

 whole of every polyzoic polyp-mass is a true entire animal, of 

 which the polypidom forms but one essential and inseparable 

 part. 



The last observation leads naturally to the inquiry if the 

 moveable processes are not attached to any distinct and separable 

 external polyp-cells*, as in Membranipora, Eschara, &c., have 

 any traces of the existence and position of the polyps been dis- 

 covered ? Now it is undoubtedly the fact that the surface of the 

 vast majority of these fossils exhibits no trace of polyp-cells. 

 And remembering that many of the most highly organized of 

 the recent Polyzoaf present very faint external traces of cells 



* The separateness, externally, of the polyp-cells is a matter more appa- 

 rent than real. The Ventriculite cells were quite as individually separate, 

 the independence of each other, therefore, of their inhabiting polyps at least as 

 great, as in Eschara, FLustra, &c. ; indeed more so, there being in the former 

 a distinct extent of the under skin between each. In the Halodactylus dia- 

 phanus the cells merely assume a hexagonal form " from their pressure upon 

 each other." This is very inferior to the Ventriculidoe : see Farre's paper 

 above-cited, p. 409, and above, p. 29. Space forbids me to enter so fully into 

 this subject as I could wish, and as its importance might render desirable 

 were it not that the line of argument would be thereby interrupted. I will 

 do no more now than recall the reader's attention to the fact of the organized 

 external integument common to the compound Ascidians, which the under- 

 skin of the Ventriculidse certainly resembles more than does the connecting 

 medium of the Eschara} and to two quotations from Dr. Johnston (Zoo- 

 phytes, p. 255 257) bearing directly on the point. "The cell," he says, 

 " is in fact the outer tunic of the polyp analogous to the envelope of the 

 compound mollusca, * * in organic connexion with the interior parts, and 

 liable to organic changes;" and in distinguishing by a marked character the 

 Polyzoa from the Anthozoa, he says, " In the latter the polyps are simply 

 developments of the common central fleshy mass, identical with it in struc- 

 ture and texture; in the former each individual is a distinct organism, and 

 the medium which binds them together, whether vascular or Hgamentous, 

 has its own peculiar character." If this is correct, there can be no doubt 

 that the Ventriculidse answer to the second description and not to the 

 first, and that indeed in a much more marked manner than do Eschara, 

 Flustra, &c. 



f I use the term Polyzoa in preference to Bryozoa, first, as having a prior 



c2 



