30d Royal Society.— 



is indicated by the circular or oval form of the cells which show 

 themselves at the surfaces of the disk, and by the singleness of the 

 row of marginal pores), each zone consists of but a single layer of 

 segments, connected together by a single annular stolon of sarcode ; 

 and the nucleus is connected with the first zone, and each zone with 

 that which surrounds it, by radiating peduncles proceeding from this 

 annulus, which, when issuing from the peripheral zone, will pass out- 

 wards through the marginal pores, probably in the form of pseudo- 

 podia. In the complex type, on the other hand (which is indicated 

 by the narrow and straight-sided form of the superficial cells, and 

 by the multiplication of the horizontal rows of marginal pores), the 

 segments of the concentric zones are elongated into vertical columns 

 with imperfect constrictions at intervals ; instead of a single annular 

 stolon, there are two, one at either end of these columns, between 

 which, moreover, there are usually other lateral communications ; 

 whilst the radiating peduncles, which connect one zone with another, 

 are also multiplied, so as to lie in several planes. Moreover, be- 

 tween each annular stolon and the neighbouring surface of the disk, 

 there is a layer of superficial segments, distinct from the vertical 

 columns, but connected with the annular stolons ; these occupy the 

 narrow elongated cells just mentioned, which constitute two super- 

 ficial layers in the disks of this type, between which is the interme- 

 diate layer occupied by the columnar segments. 



These two types seem to be so completely dissimilar, that they 

 could scarcely have been supposed to belong to the same species ; 

 but the examination of a large number of specimens shows, that 

 although one is often developed to a considerable size upon the 

 simple type, whilst another commences even from the centre upon 

 the complex type, yet that many individuals which begin life, and 

 form an indefinite number of annuli, upon the simple type, then take 

 on the more complex mode of development. 



The author then points out what may be gathered from observa- 

 tion and from deduction respecting the Nutrition and mode of 

 Growth of these creatures. He shows that the former is probably 

 accomplished, as in other Rhizopods, by the entanglement and draw- 

 ing in of minute vegetable particles, through the instrumentality of 

 the pseudopodia ; and that the addition of new zones probably takes 

 place by the extension of the sarcode through the marginal pores, 

 so as to form a complete annulus, thickened at intervals into seg- 

 ments, and narrowed between these into connecting stolons, the 

 shell being probably produced by the calcification of their outer por- 

 tions. And this view he supports by the results of the examination 

 of a number of specimens, in which reparation of injuries has taken 

 place. Regarding the Reproduction of Orbitolites, he is only able 

 to suggest that certain minute spherical masses of sarcode, with 

 which some of the cells are filled, may be gemmules ; and that other 

 bodies, enclosed in firm envelopes, which he has more rarely met 

 with, but which seem to break their way out of the superficial cells, 

 may be ova. But on this part of the inquiry, nothing save observa- 

 tion of the animals in their living state can give satisfactory results. 



