224 DR. CARPENTER'S RESEARCHES ON THE FORAMINIFERA. 



without separation of the superficial cells, while the most complete, in regard alike 

 to multiplication and to differentiation of parts, are only found among the disks at 

 present existing; and it is interesting to observe, that some of them present this 

 highest grade of development, while as yet of comparatively minute size. I am not 

 acquainted with any other Animal body, in which so wide a range of developmental 

 variation normally exists. The lower classes of the Vegetable Kingdom, however, 

 especially the group of Fungi, afford abundant examples of it*. 



67- The extreme freedom with which all the cavities of the shell mutually commu- 

 nicate, is a very marked feature in the structure of this type; and shows that the 

 several parts of the animal body are far more closely connected into one whole, than 

 they are in most of the other Forarninifera whose general plan of conformation is 

 more or less analogous. Indeed, if we were to imagine a discoidal mass of sarcode 

 to be traversed by a reticulated calcareous skeleton, somewhat resembling that open 

 areolar texture which forms the shell of the Echinida, and this network to possess 

 something of that regularity of the disposition of its successively formed parts, which 

 is presented to us in the spines of the Echinida, we should have no unapt repre- 

 sentation of the relation of the shelly disk of the Orbitolite to the animal which it 

 envelopes. There are certain Sponges which have a reticulated skeleton composed 

 of mineral matter disposed in a mode not altogether dissimilar, whilst the constitu- 

 tion of their soft bodies is essentially the same. And a remarkable connecting link 

 between Orbitolites and Sponges, seems to be presented to us in the curious Thalas- 

 sicolla discovered by Mr. HUXLEY -j~. The relations of Orbitolite to other Forami- 

 nifera have already been partly touched-on, and will become more clear hereafter, 

 when the types which most approximate to it shall have been themselves described. 



VI. Of the Species of Orbitolites. 



68. It only remains to inquire, whether the diversities which have been described 

 as existing among Orbitolites, afford any ground for assuming the existence of more 

 than a single species. With regard to the recent forms, with which, so far as they 

 are at present known, I have made myself fully acquainted, I can speak confidently ; 

 since, as I have demonstrated, the Orbitolite with a single stratum of cells (O. mar- 

 glnalls of LAMARCK, Sorites of EHRENBERG), that with a double stratum (Amphisorus 

 of EHRENBERG), and that with multiple strata (Marginopora of QUOY and GAIMARD, 

 Orbiculina Tonga of Professor WILLIAMSON), are fundamentally the same forms, deve- 

 loped in three different modes. 



69. Of the identity of all i\\e fossil species with the foregoing, I cannot speak with 

 the same confidence; since there are some of which I can only judge from figures. 

 Into the structure of that which is best known, however, and which has been com- 

 monly accounted the type of the genus, viz. the Orbitolites complanatti of the Paris 



* See especially the' recent Memoirs of M. TULASNE, in the ' Annales des Sciences Naturelles.' 

 . f Annals of Natural History, 2nd series, vol. viii. p. 433. 



