57 



standing the closeness of the folds in many species, I believe that 

 the inner parts of all the folds were polypiferous also. The in- 

 quirer familiar with recent Polyzoa will find no difficulty in 

 realizing this as true, as he will be aware that these minute crea- 

 tures are often packed in spaces so close, that it would seem to be, 

 and perhaps is, impossible that all should be protruded at the same 

 time. This fact has attracted the attention of all observers. 

 Dr. Farre notices that the individuals of Halodactylus diaphanus 

 "are so closely set that there seems to be hardly room for 

 their several operations f and that, on this account, it is often 

 "scarcely possible to make any observations upon them" even 

 with the microscope*. And the most recent writer on the 

 Polyzoa, Sir J. G. Dalyell, in his ( Remarkable Animals of Scot- 

 land/ calls attention several times to the extreme complexity of 

 the mass and to the difficulty of even microscopic observation 

 on that account t- And in the plates of both these writers 

 (pi. 25. fig. 1, Farre ; pis. 43, 44 A, &c. Dalyell) the same fact is 

 well shown. It thus becomes obvious that, in recent allied forms, 

 individuals are packed in positions quite as close as, if not closer 

 than, in any of the Ventriculida?, and in positions apparently 

 more hazardous to the free action of the individuals themselves, 

 inasmuch as the form of the recent species specially referred to 

 is less fixed and unyielding than, from the very nature of their 

 structure, the Ventriculidse have been shown to have necessarily 

 been. 



Having thus shown that there is no improbability that in fossil 

 forms the surface should have been thus closely covered, in all 

 its parts, by the polyps, I will add, that the results of positive 

 observation establish the fact that the inner parts of the folds in 

 the Ventriculidse were thus polypiferous. I have carefully dis- 

 sected several folds in specimens, both in chalk and flint, in 

 which the fold is the closest of any species, and I have found, by 

 aid of the microscope, the presence of the polyp-cells clearly and 

 unequivocally marked. 



With respect to the arrangement of the fold, the elaborate dis- 

 section of many individuals of more than thirty different forms 

 of Ventriculidse has fully satisfied me that here, as elsewhere, 

 UNITY is prevalent ; and that the fold of the membrane forming 

 the wall of the pouch is not capricious and without method or 

 principle, as at first sight it might appear. I have fully satisfied 

 myself that every form and variety of foldj which different 

 species of Ventriculidse exhibit is based on a modification of the 



* As before, p. 405. 



t See, inter alia, pp. 233, 234, as to CelMarla loricnlata. 



J Jt is necessary to distinguish the folding of the membrane forming the 



