Mr. H. J. Carter on the Structure of the Foraminifera. 325 



ten years since, at least as regards the existence of the marginal 

 plexus in Nummulites, was correct. It has been admitted by 

 Dr. Carpenter (Phil. Trans. 1859, p. 26), although he also still 

 denies the spicular structure of the cord, but will not do so any 

 longer, I think, after seeing my preparations. Dr. Carpenter 

 has, however, long since marked out the skeleton of the spicular 

 composition of the cord, as will be seen by the grooved lines on 

 the surface and the radiating ones in the transverse section, 

 represented respectively in his figures of N. laevigata (tigs. 17 

 & 15, pis. 4 & 5, Quart. Journ. Geol. Soc. vol. vi. 1850). At 

 the same time it should be remembered that the longitudinal 

 grooves do not always indicate spicules, but circumscribe spaces 

 which can be seen under a much lower power than the spicules. 

 Propagative spherules. — So recent must have been the infil- 

 trated specimens of N. Ramondi when they were imbedded, that 

 even the spherules, assumed to be propagative gemmules or 

 embryonal cells in Operculina arabica, arc exquisitely preserved 

 in a fossilized state in many of the chambers of the former, 

 where they are all spherical in shape, but vary in size, below the 

 l-2800th of an inch in diameter (PI. XVII. fig. 15 e). They are 

 not only found to exist in every part of the chamber up to the 

 umbilicus of the Nummulite, but in the primary chamber itself, 

 and may be not only seen in every part of the canal-system, but 

 (the smaller ones) also in the vertical tubes of the spiral lamina, 

 on their way out. In the infiltrated specimens of Orbitoidcs 

 dispansa they also abound throughout both the chambers of the 

 central plane and the columnar chambers, even to the centre of 

 the fossil (fig. lo). I have also seen them in the chambers of 

 Orbitolitcs Mantelli, Orbitolina lenticularis, and in Alveolina 

 elliptica ; and thus occurring so generally, there can be no longer 

 any reasonable doubt that they are what I have assumed them 

 to be, viz. "propagative agents/' but whether the product of 

 impregnation or of simple generation, remains for further research 

 to determine. In one section of N. Ramondi which I possess 

 (for I have sections by me to prove everything that I have stated), 

 there is a spherule in one of the chambers of the last turn which 

 has thrown out a second one, with a Nautiloid form of test 

 around it, indicative of Nummulites being occasionally viviparous, 

 as before stated to have been noticed in the Rotalidce by Prof. 

 Schultze (Ann. Nat. Hist. /. c. p. 320). 



Mode of growth. — This, like that of Operculina, is simply 

 spiral, with the chambers continued up to the centre or umbilicus 

 of the Nummulite. The development of the chamber commences 

 from the spicular cord, and extends outwards and inwards from 

 this point; but it is not fully formed for some time afterwards; 

 so that there are several always present in successive stages of 



