580 DE. CAEPENTEE'S EESEAECHES ON THE FOEAMINIFEEA. 



and what different species. Long before our dredging-net has swept round the British 

 coasts, we find that what was already difficult trenches on the impossible ; and when we 

 test our results by applying them to collections made in remote parts of the globe, we 

 become convinced that the limited amount of our information makes that impossibility 

 absolute. The more extensive our experience, the weaker become our convictions respecting 

 the limits of variation in any species*." 



254. The relations of the forms belonging to the family Miliolitidce have recently 

 been investigated by Mr. W. K. PARKER f on the same method of extensive and minute 

 comparison; and his results are not only in perfect harmony with those obtained by 

 Professor WILLIAMSON and myself, but even go beyond them in generality. Thus in 

 each of the genera Comuspira, ffauerina, and Vertebralina, Mr. PARKER reduces all the 

 reputed species to one, while he shows that even their generic differences are really but 

 of small account. And he not only in like manner reduces all the reputed species of 

 the genus Miliola to the level of varieties, but brings down to the same rank the reputed 

 genera Spiroloculina, Biloculina, Triloculina, and Quinqueloculina ; the differences be- 

 tween which, arising from asymmetrical growth, and from variations in the form and 

 number of the chambers, cannot be regarded as even of specific value, the Milioline 

 plan of construction being preserved throughout. " If," he remarks, " the forms kept 

 themselves as distinct as those represented in the diagrams, a naturalist might be 

 excused for regarding them as distinct types ; but between any two of these there may 

 readily be found innumerable gradations, in large and small specimens, in the smooth 

 and ornamented, in the shelly or the sanded, in attenuated and in distended individuals, 

 and in specimens with symmetrical or non-symmetrical, or with two- or three-sided 

 shells." I may add that I am fully prepared to endorse these conclusions; since they 

 are entirely borne out by my own experience as to such forms of the Milioline type as 

 have fallen under my notice. 



255. In the large group of Nodosarince which has been carefully studied by Messrs. 

 T. EUPERT JONES and W. K. PARKER, those gentlemen have felt themselves justified 

 on the like grounds in reducing a multitude of reputed genera and species to a single 

 type. Between the nautiloid Cristellarm and the straight moniliform or rod-like Nodo- 

 sarice, which agree in essential characters of structure and mode of growth, they find 

 such a continuous series of connecting links, that no line of demarcation can be any- 

 where drawn, the straight, the curved, and the spiral forms passing gradationally one 

 towards another. And the extreme forms being thus brought together, the various 

 intermediate grades which have been distinguished by systematists under the generic 

 names of Glandulina, Lingulina, Dentalina, Rimulina, Vaginulina t Planularia, Margi- 

 nulina, Dimorphina, Flabellina, and Frondicularia, necessarily fall into the same 

 category J. 



* Introd. pp. k, x. t Transactions of the Microscopical Society, 1858 (New Scries, vol. vi.), p. 53. 



J Annals of Natural History, Nov. 1859, p. 477 ; and Quarterly Journal of the Geological Society, Aug. 

 1860, p. 302, and Nov. 1860, p. 454. 



