196 Mr. n. C. Sorby on the Organic Origin 



sophical Society, on the 2nd of October, in which I showed that 

 the so-called crystalloids of the chalk are not of crystalline or 

 concretionary origin, but are similar to ovoid bodies forming 

 part of spherical cells in some respects analogous to the cells of 

 Foraminifera. 



Nearly two months after this, I had the pleasure of making 

 the acquaintance of Dr. Wallich, who had just returned from 

 his voyage in H.M.S. 'Bull-dog,' and found that he also had 

 discovered the true origin of the Coccoliths, as described at p. 13 

 of his " Notes on the presence of Animal Life at vast Depths in 

 the Sea, &c.,'' published for private circulation in November 

 1860, without having been aware of their important relation to 

 chalk. Mr. Roberts, however, in his paper on " High and Low 

 Life*," when alluding to Dr. Wallich's interesting discoveries, 

 says, " Their discovery in a living state in this ooze is of high 

 geological importance; for microscopical investigation, under- 

 taken by Mr. Sorby, proves their existence in chalk-rocks, 

 associated there, as they are in this North iVtlantic Ocean, with 

 Globigerinse. Indeed, chalk itself is seen to be little else than 

 a compacted mass of Foraminifera-shells, whole and fragmentary, 

 and may be best described by using the very words by which 

 Dr. Wallich introduces to science this recent deposit. '^ 



Having thus given a history of the subject, I will proceed to 

 describe some of the facts I have observed, but at the same time 

 shall not attempt to give anything like a complete account of 

 the microscopical structure of chalk, which could not be done 

 without a number of illustrations. Moreover, there are some 

 interesting questions requiring further investigation, which I 

 hope to describe in detail when treating on the microscopical 

 structure of rocks in general. The drawings of Coccospheres 

 and Coccoliths which I made nearly a year ago agree very closely 

 with the figures accompanying Dr. Wallich's paper (pp. 53 & 54). 

 I must confess that, as he justly observes, one is tempted to 

 conclude that there is some connexion between Coccospheres 

 and Globigerinse ; but, at the same time, I feel inclined to think 

 that they may be an independent kind of organism, related to, 

 but not the mere rudimentary form of, Foraminifera. Their 

 optical properties are entirely different. Each cell of Globi- 

 gerinse, when alone or attached, gives a splendid well-defined 

 black cross and coloured rings when examined with polarized 

 light, which is readily explained by the fact of the shell being 

 made up of minute crystals of calcite, arranged with their prin- 

 cipal axis perpendicular to the surface of the shell. No such 

 cross is, however, seen in the case of Coccospheres; and the 

 cell-wall between the Coccoliths has such a very weak depolar- 

 * 'Geologist,' 18(Jl,iv. 1. 



