Reproductive Processes of Sponges. 375 



Still, while attempting this reconciliation, it is necessary to 

 bear in mind that the sponge-cell is unceasingly polymorphic 

 except under the resting-form, which is spherical, and that this 

 polymorphism enables it to assume a monadic monociliated 

 form at one time and immediately afterwards almost any 

 unciliated amoeboid one that can be conceived — apparently 

 amalgamating with its neighbours into a homogeneous mass, 

 yet at any moment ready to separate and resume any of its 

 wonted forms under favourable circumstances. 



In 1849 I noticed that the " sponge-cell itself frequently 

 contained pieces of Conferva' within duplicatures of its cell- 

 wall, and other matters " similar to what might be seen in 

 the " proteus "= Amoeba (no. 3, p. 94) 5 also that the " living 

 sponge " presents " ejecta " on its surface, which " consist 



9. 1867. James-Clark, H. "Spongiae ciliatae as Infusoria flagellata." 

 Boston Soc. Nat. Hist. Mem. vol. i. pt. 8, pis. ix. and x. 



10. 1869. Carter, II. J. " On GreyeUa cyathophora, a new Genus of 



Sponges." Ann. fy Mag. Nat. Hist. ser. 4, vol. iv. p. 189, 

 pi. vii. 



11. 1872. Hackel, E. 'Die Kalkschwamine.' 3 vols. (Two text, 



one Atlas.) 



12. 1874. Carter, II. J. "On the Nature of the Seed-like Body of 



Spongilla ; on the Origin of the Mother-cell of the Spicule ; and 

 on the Presence of Spermatozoa in the Spongida." Ann. fy 

 Mag. Nat. Hist. ser. 4, vol. xiv. p. 97, pi. x. 



13. 1874. . u Development of the Marine Sponges from the ear- 



liest recognizable Appearance of the Ovum to the Perfected 

 Individual." lb. vol. xiv. p. 321, pis. xx.-xxii. 



14. 1875. Schulze, F. E. " Ueber den Bau und die Entwicklung von 



Sycandra raphanus, Hackel." Zeitschrift fur loissenschaftliche 

 Zoologie, Bd. xxv. Suppl. Taf. xviii.-xxi. 



15. 1876. Barrois, Ch. " Embryologie de quelques Eponges de la 



Manche." [Inaugural Thesis.] Annates des Sci. Nat. Zoologie, 

 ser. 6, t. iii. 



16. 1876. Keller, C. ' Untersuchungen iiber die Anatornie und Ent- 



wicklungsgeschichte einiger Spongien des Mittelmeeres. Ein 

 Beitrag zur Losung der Spongienfrage.' 4to. Basel, 1876. 

 Taf. i. u. ii. 



17. 1877. Schulze, F. E. "Untersuchungen iiber den Bau und die 



Entwicklung der Spongien, — Die Oattung Halisarca.^ Zeit- 

 schrift fur wissenschaftliche Zoologie, Bd. xxviii. Taf. i.-v. 



18. 1878. . Untersuchungen iiber den Bau und die Entwicklung 



der Spongien. — Die Metamorphose von Sycandra raphanus. 

 lb. Bd. xxxi. p. 262, Taf. xviii. und xix. 



19. 1879. Balfour, F. M. " The Morphology and Systematic Posi- 



tion of the Spongida." Quarterly Journal Microscopical Science, 

 no. 73, p. 103. 



20. 1879. Metschnikoff, E. " Spongiologische Studien." Zeitschrift 



fur ivissenschaftliche Zoologie, Bd. xxxii. p. 840, Taf. xx.-xxiii. 



21. 1879. Carter, II. J. " Contributions to our Knowledge of the 



Spongida." Ann. 8f Mag. Nat. Hist. ser. 5, vol. iii. p. 284, 

 pis. xxv.-xxix. 



