
1905.] . the English Species of Nummulites, etc. 317 
_- By this result additional proof is given of de la Harpe’s conclusion, founded 
on the mode of occurrence in the beds, and on structural features of the tests 
of the two forms, that these are in each case truly members of “a pair,” 
or, aS we now say, are related as alternating or recurring forms in the 
life-history of a species. 
By (2) and (3) the two modes of reproduction come into marked contrast : 
the asexually produced megalospheres being approximately proportional in 
size to the protoplasmic volume of the parent, while the microsphere, 
probably arising as a zygote, 1s uniformly small throughout. 
4, In several of the species examined, as the microspheric member of the. 
cycle preponderates in the life-history, the megalospheric member decreases, 
not only in proportion to the size of the microspheric form, but in proportion 
to the megalospheric members of other species in which the two forms attain 
approximately equal sizes. 
In conclusion, I wish to express my thanks to Dr. Harmer, the Superin- 
tendent of the Museum of Zoology in this University, for the free use he has 
allowed me to make of the ample stores of material in the Brady Collection ; 
and to Professor Hughes for kindly placing at my disposal the specimens of 
N. Orbignyt var. elegans from Huntingbridge, contained in the Sedgwick 
Museum; also to Mr. H. Keeping of that Museum, whose knowledge of 
the beds of the Hampshire Basin has considerably assisted me. 
I have to acknowledge the helpful advice I have received from my friend 
Mr. A. Harker in preparing the table on p.311. To Mr. R. B. Newton, of the 
British Museum, I am also indebted for his assistance when examining the 
specimens in the Sowerby Collection there contained. 
The photographs with which this paper is illustrated were made with the 
kind help of my brother, Mr. W.T. Lister. They were done with the excellent 
Zeiss instrument in his possession. 
LITERATURE QUOTED. 
Brady, H. B., Report on the Foraminifera collected by H.M.S. “Challenger ” (1884). 
2. Wanden Broeck, E., “Comment faut-il nommer les Nummulites, en tenant compte 
de leur dimorphisme ?” ‘ Bull. Soc. Belge d. 1. Géologie,’ vol. 10, fasc. 4 (1896), 
p. 50. 
3. Douvillé, H., “ Etudes sur les N ummulites, lre Note,” ‘ Bull. Soc. Géol. de France,’ 
4 sér., vol. 2 (1902), p. 207. 
4, Fisher, O., “On the Bracklesham Beds of the Isle of Wight Basin,” ‘Q. J. Geol. 
Soc.,’ vol. 18 (1861-2), p. 65. 
5. De Ja Harpe, Ph., “Etude des Nummulites de la Suisse, et revision des espéces 
Eocénes des genres WVummulites et Assilina,” ‘Mém. Soc. Paléont. Suisse,’ 
vols. 7-10, 1881-3. 
ie 
