FORAMINIFERA. 891 



extracapsular protoplasm of many Radiolaria. The pseudopodia are 

 organs of locomotion as well as of alimentation. Foreign bodies when 

 sufficiently small may be drawn within the test ; but they are very 

 generally, in many instances indeed necessarily, digested outside it. 

 Minute non-contractile vacuoles have been observed in Shephear delta and 

 Spirillina ; a single contractile vacuole in some species of Gromia, in 

 Microgromia and Diaphoropodon. It is said that the vacuoles of Lieber- 

 kuhnia eventually come to the surface and burst. Vacuoles which change 

 in shape and disappear, whilst others appear in their stead, have been 

 observed in some marine genera, e. g. the Miliolid Biloculina (Biitschli). 



All Foraminifera properly examined have been found to possess a 

 nucleus, and at first one only a fact to be carefully noted, as showing that 

 polythalamous genera are neither truly segmented nor colonial \ In them 

 the nucleus appears to wander by degrees into the outer chambers from the 

 primordial chamber where it is primitively situated. Both mono- and 

 poly-thalamous genera however become multinucleate sooner or later, and 

 the nuclei are thereupon scattered through the chambers if there is more 

 than one. The increase of the nuclei in number is probably connected 

 with reproduction (infra). The nucleus has a membrane with contents 

 usually described as homogeneous or finely granular, but in well-prepared 

 specimens there is a distinct chromatin network, with one or more nucleoli 

 (Butschli). In Trochammina (Rotalina) inflata, and in an Ovulina, one 

 half of the nucleus has been found to consist of chromatin, the other of 

 a non-staining substance. 



Binary fission has been observed only in Lieberkiihnia and Micro- 

 gromia 2 . In the former it is transverse, and the delicate test undergoes 

 division with the body ; in the latter it is either transverse or longitudinal. 

 When it is transverse the hinder part quits the test and becomes either 

 amoeboid or ovate and biflagellate. When longitudinal, both parts are in 

 connection by their pseudopodial peduncles ; one quits the test but re- 

 mains a member of the colony ; it sometimes undergoes a previous sub- 

 division into two. Portions of the disc in Orbitolites, accidentally broken 

 off, continue to live and form new and completely concentric annuli. A 

 mode of reproduction to be regarded as spore-formation (?) has been 

 observed in various calcareous Foraminifera Miliolina, Peneroplis, Orbi- 

 tolites covnplanata^ Cristellaria, Spirillina, and a Rotalid, representatives of 

 both imperforate and perforate genera. There appear within the adult 



1 The monothalamous Lieberkiihnia , Haliphysema and Spirillina are known only in the multi- 

 nucleate state. 



2 It is not likely that abortive attempts at fission are indicated in the double shells seen some- 

 times in Lagena, the partially divided coils of Polystomella, the bifid discs of Orbitolites com- 

 planata, or the half-discs set on the normal discs in that Foraminifer. They are probably simply 

 irregularities of growth. To what an extreme such irregularity may be carried, see von Roboz' 

 account of Calcituba in SB. Wien. Acad. 88, Abth. i, 1884. 



