PROTOZOA. 
669 
tility iu the stalk of VorticcUa, is led to believe that the contraction of the 
muscular libre of the stalk corresponds with the state of repose of the 
spring ; it is the immediate consequence of its elasticity. The elongation of 
the fibre is the result of the forced extension of the spring by a movement 
dependent on the act of nutrition, and acting during the apparent repose 
of the contractile organ. As soon as the force of this antagonistic force is 
exhausted, elasticity, recalling the muscle to its natural form, produces the 
so-called movement of contraction. 
II. SPONGIIDA. 
The following is a synopsis of the families proposed by Dr. 
J. E. Gray (/. c . p. 502 seq .) 
Subclass I. VOJIIFJIOJRA SILICEA. 
Section I. Mal ACOSroRiE. Reproduction hy ova contained in a thin mcni- 
hranaceous ovisac not strengthened hy siliceous spicules, or hy gemmules 
scattered in the body of the sponge. 
Order I. CORALLIOSPONGIA. Sponges hard, coral-like, entirely formed 
of siliceous spicules auchylosed together by siliceous matter into a net- 
work. Mass covered with a thin coat of sarcodo when alive. 
Family 1. DACTYLOCALYCiDiE. Sponge massive, expanded or flabellate, 
reticulate, angular. 
Genera : — Dactylocolyx, Stutchbury, 1841 : J), pumicea, Stutch. (Gray 
1. c. pi. 27. fig. 2). Miliusia, Gray, 1850 : M. callocyathes, Gray, P. Z. S. 
1869, p. 439, Radiata, pi. 10. MacAndrewia, Gray, 1869 : M, azorica, Gray, 
P. Z. S. 1869, p. 438, Radiata, pi. 15. Farrea, Bowerb. : F. orca, Bowerb, 
Fam. 2. ApimocALLiSTiDiE. Sponge tubular; tubes closed with a reti- 
culated lid; parietes formed of agglutinated siliceous spicula, with 
round horizontal lateral pores ; inner surface strengthened with clustered 
bundles of elongated spicules. 
Genus: — Aphrocallistes, Gray: A. heatrix, P. Z. S. 1868, p. 114, Radiata, 
pi. 11. 
Order II. KERATOSPONGIA. Sponge elastic. Skeleton formed of horny 
netted fibres, generally without, but sometimes more or less strength- 
ened with, minute siliceous spicules or grains of sand. 
Fam. 3. SpoNOiADiE. Skeleton formed of one kind of horny reticulated 
fibres, not enclosing any spicules or sand. 
Genera : — Spongia, Linnasus : S. officinalis. Spongionella, Bowerb, : S.puU 
chella, Bowerb. Brit. Sp. i. p. 206. Cacospongia, Sdt. : C. mollior, Schmidt, 
Spong. Adriat. p. 27. Sijdwnia, Blainv.: S. typum, Blainv. Man. Act. p. 630. 
Apylysina, Sdt. : A. acrophoha (Nardo), Schmidt, Spong. Adriat. p. 26. Fc- 
rongia, Bowerb. : V.jistidaris (Lamk.), Bowerb. .Brit. Sp. i. p. 209. AulisJda, 
Bowerb. : A. howerhanhii (Gray), 1. c. p. 610. 
Fam. 4. IIirciniap.®. Sifeleton formed of two kinds of horny fibres, — the 
one thick, and with a central line of spicules or grains of sand within, 
reticulated, forming the base of the skeleton ; the other very slender, 
forming radiating spicular tufts, which do not anastomose. 
Genera ; — Hircinia, Sdt. : H. Jlavescens, Schmidt, Spong. Adriat. p. 33. 
