September, 1910. 



KNOWLEDGE. 



379 



successive chambers, becoming constricted in order 

 to pass through the pores connecting the chambers. 

 In full-grown specimens the nucleus was usually 

 found midway between the earliest and the latest 

 chamber. Later still the nucleus was observed to 

 break up and disappear, and a great number of 

 nucleoli made their appearance in the protoplasm. 

 Each of these nucleoli attracted to itself, and 

 became surrounded by a minute rounded portion of 

 protoplasm. The nucleoli then divided by karyo- 

 kinesis, and subsequently the whole contents of the 

 shell poured out as active flagellate zoospores, and 

 swam a\\ay. 



Here the direct observation of the life-histor\- 

 ended, for Lister was unable to follow up the move- 

 ments of the active zoospores. But there is ever\- 

 reason to believe that after a free swimming existence 

 the zoospore settles down as a microsphere, and so 

 commences the life cycle anew . Lister points out 

 that the zoospores are on an average less than one- 

 third of the size of a microsphere, and he records 

 an observation of Schaudinn, who found that when 

 cover-glasses were suspended in an aquarium with 

 living Polystomellac. so that thev hung free from the 

 sides and bottom, \'oung microspheric specimens 

 made their appearance on them in two days. He 

 points out that PolysfomeHa can only crawl over 

 surfaces and cannot swim, and that the colonisation 

 of the coverslips under such conditions implies 

 the existence of an earlier free-swimming stage, such 

 as the zoospores supph. Moreover, he points out 

 that the difference between the size of the zoospores 

 and the microspheres would be explained if a sexual 

 conjugation of the zoospores took place, such as has 

 been observed in the case of other organisms pro- 

 ducing motile spores. 



Lister concludes from his observations that the 

 megalospheric and microspheric stages represent an 

 alternation of generations. While the megalospheric 

 generation is produced asexually from a micro- 

 spheric or, occasionally, a megalospheric parent, the 

 microspheric generation arises sexually from the 

 conjugation of two similar zoospores, probabh- derived 

 from different parents. 



It is difficult to write with certainty as to the 

 distribution of PolystomeUa crispa, owing to the fact 

 that the records of this species have been confused 

 with those of its allv P. niacella Fichtel and Moll, sp. 

 Bradv states that it has been recorded from as far 

 North as Disco Bay, Greenland, and as far South as 

 Kerguelen. Probably, however, these extreme records 

 refer to P. macella (which certainly has a wider 

 range than P. crispa), although Brady, for some 

 unexplained reason, fixes the Mediterranean as 

 the Northern limit for that species. It would 

 appear, however, from our own observations that 

 P. crispa is to be found from the Equator to 

 Fetlar in the North of Shetland at any rate. Goes 

 records it from the Skagerack and the Swedish coast. 

 South of the Equator it extends to the Southern 

 Island of New Zealand, but apparently this is its 

 southern limit as Chapman does not record it from 



" The Snares " (which are at the extreme south of 

 the Islands), in his recent paper on Sub- Antarctic 

 Foraminifera. In depth it ranges from shore pools 

 to three hundred and fifty-five fathoms, according 

 to Brad\'. W^e ourselves have found a single 

 specimen in a dredging taken b\- the "Challenger," 

 off the Azores, in one thousand fathoms, but this 

 ma\" be an exceptional individual, derived from a 

 piece of floating alga. 



PolystomeUa crispa was one of the first Foramini- 

 fera to attract the attention of those conchologists 

 who studied what they considered to be minute 

 Mollusca. It was figured and described by Plancus 

 so far back as 1739, and again by Gualtieri in 1742. 

 It was observed by the great Linnaeus to whom it 

 owes its name. Needless to say it has suffered 

 considerably from the species-mongers in the 

 interval since Linne christened it, and a complete 

 Bibliograph\- of the species would extend to a 

 considerable length. .\s, however, most of the 

 s\-nonvms refer only to feeble or intermediate 

 varieties of the t\pe. we confine our selection to the 

 most important records. Those interested in the 

 subject can extend the list to very much larger 

 dimensions by referring to Mr. Sherborn's invaluable 

 Index. 



BIBLIOGRAPHY. 



" Conui Haminonis orbiculatum," Plancus, 1739, De Conchis 



minus notis Liber, p. 10, pi. i. fig. 2. 

 " Nautilus minimus " Gualtieri, 1742, Index Testarum Con- 



chyliorum, and so on, pi. xi.x, figs. A.D. 

 Xaiifilits crispiis Linne, 1757. System Nat., 12th ed., 



p. 1,162-275. 

 " Nautilus spiralis geniculis crenatis." Walker & Boys, 1784, 



Testacea. minuta, and so on, p. 18, pi. iii. fig. 65. 

 ■■ Nautili striati com mimes (crispi Linnaci)." Soldani, 1789, 



Testaceographia, vol. i. pt. i. p. 54, pi. xxxiv, figs. c. c. e. e., 



C.H.I. 

 PolystomeUa OK'cniann d'Orbigny, 1S39, Foram. .\mer. 



Merid.. p. 30, pi. iii, figs. 3, 4. 

 PolystomeUa lanieri d'Orbignv, 1839, Foram. Cuba, p. 74, 



pL vii, figs. 12, 13. 

 PolystomeUa flexuosa d'Orbigny, 1846. Foram. Foss. Vienne, 



p. 127, pi. vi. figs. 15. 16. 

 PolystomeUa crispa (LinncI, \\'illiamson, 1849, Trans. Mic. 



Soc. London, vol. ii, p. 159, pi, xxviii. 

 PolystomeUa strigillata SchuUe, 1854, Org;m. Pol)'thal., 



p. 64, pi. iv. 

 PolystomeUa crispa (Linnel, Williamson, 1858, Recent 



Foram. Gt. Britain, p. 40. pi. iii, figs. 78-80. 

 PolystomeUa crispa (Linnel, Carpenter, 1862, Introd. Foram., 



p. 278, pi. xvi, figs. 4-6. 

 PolystomeUa crispa (Linne), Parker & Jones, 1865, Phil. 



Trans., vol. civ, p. 399, pi. xiv, fig. 24. pi. xvii, fig. 61, a.b. 

 PolystomeUa crispa (Linne). Brady. 1884, Foram. Challenger, 



p. 736. pi. ex, figs. 6, 7. 

 PolystomeUa crispa (Linne), Brady, 1887, S\-nopsis Brit. 



Foram. in Jour. R. Mic. Soc. pt. 6, p. 926. 

 PolystomeUa crispa (Linne), Goes, 1894, Synopsis Arctic and 



Scandina\ian Foram. in Kongl. Svenska Vetenskaps- 



Akad. Handl., Band 25, No. 9, p. 102, pi. xvii, 



figs. 820, 821. 

 PolystomeUa crispa (Linne). J. J. Lister, 1895. Contributions 



to Life History of Foraminifera in Phil. Trans., 



vol. 168, B., p. 414-431, pi. vi-viii, figs. 1-3, 5-33. 

 PolystomeUa crispa (Linne), J. J. Lister, 1903, The Foram- 

 inifera in Ray Lankester's Treatise on Zoologj-, part 1, 



fasc. 2., sect. I, p. 62-73. 



