OF THE PROTOZOA . RKTZOPODA. 239 



ha\ing the cells spirally arranged, but each one occupying only one-half the 

 circuit. 



The three sections proposed by Schultze are — 1. shells disposed in recti- 

 linear series or in a slightly- curved line, Bliahdoidea ; 2. those coiled in a 

 spii'al, HeUcoidea ; 3. those irregularly aggregated, Soroidea. The first of 

 these corresponds to the SticJiostegia of D'Orbigny ; the second includes all 

 the remaining orders of that wiiter ; whilst the third section is represented 

 by a small number of species, previously itn mentioned, vrhich Schultze unites 

 in the genus Acervulina. 



^\Tiat structural peculiarities should be employed to determine species, is a 

 question now much mooted \\dth respect to the Foraminlfem. In reference 

 to this subject, Dr. Carpenter (in the annual address at the Microscopic So- 

 ciety, Feb. 1855) obsei-ved " that a large proportion of the species, and even 

 of the genera, which have been distinguished by systematists, and especially 

 by M. D'Orbigny, have no real existence, being nothing else than individual 

 varieties." This error is at once accoimted for by M. D'Orbigny's mode of 

 proceeding (as stated) : "for that, in examining any new collection, he set 

 an assistant to pick out the most divei^gent forms, and then described all that 

 might prove new to him as distinct species, mthout troubling himself in the 

 least about those connecting links, the existence of which should have at once 

 convinced him that he was following an altogether wrong method. Through- 

 out the whole of his labom\s on the group, in fact, I find the influence of the 

 erroneous ideas which he originally entertained ^^ith regard to the natiu-e of 

 the animal of the Fomminifem ; for in the formation of his orders, as well 

 as of his genera and species, he has proceeded as if the characters of the tes- 

 taceous skeleton were of the same distinctive value when its construction is 

 due merely to the solidification of the siuface of a minute fragment of animal 

 jelly, which is subject to an almost indefinite variation both in size and in 

 shape, as when it belongs to a moUusk of high organization, the plan of 

 whose conformation is definitely fixed .... When a collection is brought to- 

 gether containing large numbers of individuals of one generic type, which 

 appear, however, to belong to several distinct species, it very commonly hap- 

 pens that, although it would be easy to make 6, 8, 12, or 20 species by 

 selecting the most divergent forms, yet, when the attempt is made to sort 

 the entire collection under these tj^pes, only a part of it can be unhesitatingly 

 arranged aroimd them as centres, the remainder being transitional or inter- 

 mediate forms, for which another set of species must be made, if the principle 

 of separation be once adopted. In fact, to such an extent does individual 

 variation often go, that (as in the case of the human race) no two specimens 

 are precisely alike, and there is no satisfactory medium between grouping 

 them all as varieties of one species, and making every individual a species, which 

 is manifestly absurd." 



The error of D'Orbigny has not escaped Schultze's notice ; for in his chapter 

 on classification he has repeatedly pointed out the insufiiciency of the charac- 

 tei-s on which that observer relied in framing his species, genera, and families. 

 For instance (p. 52), he points out the erroneous separation of the Stichoster/ia 

 (D'Orb. j into two families, according to the equilateral or inequilateral con- 

 dition of the shell. And further on, he remarks that the variations elevated 

 by D'Orbigny to the rank of specific distinctions are merely accidental diver- 

 sities in growth, connected together by every intermediate variety. Hence, 

 for example, he combines the genera Trilocidina and Quinquelocidina (D'Orb.) 

 into one genus MilioJa, and the Orhitoides and Orbitulina (D'Orb.) into a 

 single genus Orhitolites. Various other illustrations might be adduced, for 

 instance, the family Nautiloidce ; but it is unnecessaiy to muluply them. It 



