130 Mr. C. Davios Slierboru, on the 



being divisible by size ; and farther, that tlie smaller shells 

 invariably begin with a large chamber, while the larger shells 

 either have no recognisable central chamber, or one of very 

 small size.:;- De la Harpe considered tliese two forms as distinct 

 species. MM. Mmaier-Chalmas and Schhimberger took up this 

 question, and came to the conclusion that the difference was one 

 of development only, and that the " pairs " were two forms of 

 the same species. De la Harpe, in a later paper, suggests that, 

 had it been a fact that sex existed amongst the Foramhiifera, he 

 would have been inclined to regard this difference as of a sexual 

 nature. ]\lr. Patrick Geddes is inclined to agree with this later 

 siiggestion of De la Harpe. Similar large and small initial- 

 chambered forms amongst the Milivlin/e have been described 

 by M]\[. Munier-Chalmas and Schhimberger. 



So little being known of the animal, the only clxssification 

 possible was that of shell-sti-ucture. Many schemes have been 

 proposed, the most simple being that of Rupert Jones, based on 

 previous observations by himself and others. Prof. Jones divides 

 the Foraminifera into Porcellana or Imperfoeata (thick and im- 

 perforate shell-wall), L'i»nns}iira, Miliolina, &c. ; Arenacea (sandy 

 tests), Litiiola, Te.i-tulaiin, &c. ; HYALI^^A or Perforata (thin, 

 vitreous, and perforate shell-wall), Loijena, Nudiimriii, lintalia, 

 &c., — by far the largest number. Roughly speaking, all the 

 Foraminifera can be relegated to one or other of these three 

 sections. Those interested in the farther discussion of classifi- 

 cation will find the best-known schemes criticised and explained 

 in the opening pages of Brady's ' Challenger ' Report, 1884. 



The further classification of the Foraminifera into genera and 

 species has also been carried out on external features, and it is 

 often difficult to understand how certain forms can possibly hold 

 good as genera or even species, but, although they pass in many 

 instances so completely from one into another, we know they do 

 not differ in form and ornament alone, but in habit, occurrence, 

 depths at which they live, modes of life, &c. " Whether species 

 or not," says Mr. Brady, "they have distinctive characters, and 

 it is necessary they should receive distinctive names." 



It has been the custom of some authors to name every variety 

 as a species ; with others to group many varieties around one 

 marked form. It is hard to say which is the more correct 

 method; as often, in geological research, a particular variety of 

 a so-called species is characteristic of a stratum. The work of 

 elucidating and explaining the meanings of older authors has 

 been carefully and elaborately done by Parker and Rupert Jones, 

 and later on by Brady, in a series of articles contributed to the 

 'Annals and Magazine of Natural History' between 1859 and 



• A iaet previously observecl by Parker aucl Jones. 



