Miliolina; and in other Foraminifera. 403 



PerilocuUna, Massilina, SptroIocuNna, and Sigmo'ilina ; be- 

 sides others, as — Nodosaria, Dentaltna, Cristellaria^ Sipho- 

 generinttj Orhulina, Rotalina, and Amphistegina (see E. Van 

 den Broeck, Bull. Soc. Beige Geol. Paleont. et Hydrolog. 

 vol. vii. 1893, pp. 6-41). 



In 1884 H. B. Brady (in the Eeport ' Challenger,' pp. viii 

 and ix) gave a succinct account of dimorphism in the two 

 different senses in which it had been applied by rhizopodists 

 from the time of d'Orbigny to that of Munier-Chalmas and 

 Schlumberger. 



Signor C. Fornasini has noted the existence of the two 

 forms above-mentioned, " A " and " B," in Biloculina *, 

 i^odosaria^^ and Frondicularia {. 



In his ' Elements de Paleontologie,' part i. 1893, pp. 83- 

 86, M. Felix Bernard gives a resume of the views on 

 " Dimorphism " published by MM. Munier-Chalmas and 

 Schlumberger, with a page of figures wrongly numbered for 

 the most part. 



Dr. A. Goes notices § that there are intermediate forms 

 between those with large and those with small initial 

 chambers, which are varying conditions of evolution ; and he 

 regards the successive embryonal, larval, and adult stages, 

 such as are visible in Frondicularia, as constituting poly- 

 morphism rather than dimorphism in Foraminifera. 



The persistence of the original or initial style of growth in 

 adults may be normal in evolution ; but the recurrence of 

 en)bryonai after an advanced style of growth in adult forms 

 appears to be deterioration by reversion to early conditions, 

 and the features arising from the latter process can scarcely 

 be regarded as really specific characters ; and yet sometimes 

 they have been taken as of even generic value (as Amphi- 

 coryne). Where, however, one type of growth is succeeded 

 by that of another type, as Cristellaria by PoJymorphina (see 

 Goes, K. Sv. Vet.-Akad. Handl. vol. xix. no. 4, pi. lii. fig. 40 ; 

 and Brady, Eeport 'Challenger,' pi. Ixxi. fig. 10), there may 

 appear to be some reason for recognizing a specific status. 



zool. France, vol. xi. 1886, pp. ,544-557 ; M6tn. Soc. zool. France, vol iv 

 1891, pp. 542-578, vol. vi. 1«93, pp. 57-80. 



* Boll. Soc. geol. Ital. vol. v. fasc. ii. 1886, p. 261, pis. iv. and v. 



t Op. cit. vol. vi. fasc. i. 1887, p. 29, footnote (with M. Schliimberger's 

 remarks) ; op. cit. vol. ix. fasc. ii. 1890, pp. 345-347, pi. viii. 



\ Mem. R. Accad. Sci. Istit. Bologna, ser. 5, vol. i. 1891, pp. 480-483 

 and plate ; Signor D. E. Dervieux has also remarked A and B Frondicn- 

 laricB, Bull. Soc. geol. Ital. vol. xi. fasc. ii. 1893, pp. 241 &c., pi. iv. 



§ Bihang Vet.-Akad. Handl. (Stockholm), vol. xv, part 4, no. 2 (14 

 pages and 1 plate), 1889; and in the Annuaire geol. &c. vol. viii fa«c 4 

 1893, pp. 844-84(i, and vol. ix. 1894, pp. 911-913. " ' ' 



