SPONGIJ]:. 



[ 603 ] 



SPONGIOLES. 



of this gelatinous substance are examined 

 under the microscope, they exhibit Amaha- 

 hke processes in motion. 



The fibres have been described as solid 

 and as tubular. Those of the common 

 sponges appear under the microscope to be 

 solid ; but when treated with sulphuric acid, 

 it is easily seen that they consist of two 

 parts, an outer tubular portion, which is 

 contracted in length by the acid, and an 

 inner cylindrical thread, which is not so con- 

 tracted, but usually becomes elegantly wavy 

 or spiral from flexion, frequently also partly 

 protruding from the cavity of the outer por- 

 tion in broken fibres, and resembling PI. 21. 

 fig. 22. 



The spicula are of various forms (PI. 37, 

 the lettered figures), and either scattered 

 through the substance, or arranged in bun- 

 dles forming spurious fibres; sometimes 

 projecting more or less from the surface 

 (PL 37. fig. 8). In some sponges they are 

 absent, and in one genus they are replaced 

 by gravel. There is some obscurity about 

 the gravel, however, for its particles are de- 

 scribed as being uncrystalline, and as neither 

 siliceous nor calcareous ! 



In some sponges an external membrane is 

 present, and this has been observed to exhi- 

 bit a reticular or cellular appearance, from 

 the presence of fine reticular fibres. 



Sponges are mostly marine, rarely aquatic. 

 In the natural state they possess lively co- 

 lom-s, which appear in some instances to 

 arise from the presence of granules of colom*- 

 ing matter, probably chlorophyll, in others 

 from iridescence. They usually grow in 

 groups upon rocks, shells^ polypes, sea- 

 weeds, &c. 



A vascular system has been described as 

 existing in some marine sponges, consisting 

 of anastomosing tubes or vessels enclosed in 

 a membranous sheath surrounding the horny 

 fibres, and containing minute corpuscles. 

 We regard the existence of this system as 

 problematical. 



Sponges appear to be propagated in three 

 ways : by division or the growth of detached 

 portions of the parent, which appears rather 

 probable than proved ; by the formation of 

 ciliated gemmules; and by the production 

 of internal oviform bodies, one kind being 

 analogous to winter-ova, and also called 

 gemmules. 



The ciliated gemmules, which are not of 

 general occurrence, are yellowish, oval, nar- 

 rowed at one end, and covered, except at this 

 part, by vibratile cilia. They are mostly 



formed in spring, and after swimming about 

 for a time, become fixed to some suitable 

 spot, and undergo development. 



Of the other reproductive bodies, one 

 kind consists of roundish or ovate masses, 

 containing spicula, and resembling the parent 

 in structure, either lying loose in its sub- 

 stance or adherent to the horny fibres, and 

 escaping at its death and solution, to acquire 

 maturity. 



The bodies resembling winter-ova are 

 round or ovoid, with a funnel-shaped de- 

 pression on the surface communicating vnth. 

 the interior. At first these lie in a cavity 

 formed by condensed surrounding substance ; 

 subsequently a membrane presenting a hexa- 

 gonal reticular structure is formed around 

 them, upon which a crust of spicula is after- 

 wards deposited. When expelled from the 

 body of the parent, they are motionless; 

 they then swell up, burst, and the minute 

 locomotive germs escape. These now ex- 

 hibit Am(£ha-\\kQ processes, and take on an 

 independent life. 



No nucleus has been detected in sponges, 

 the soft substance appearing to correspond 

 to cell-contents. 



Sjjonges are probably nourished by en- 

 closing Algae, &c. in their substance in the 

 same manner as Amoeba. This has been 

 seen to take place in the case of the young 

 animals developed from the ^\inter-ova. 



The genera and species have been so 

 loosely and unintelligibly characterized, that 

 the descriptions would be useless to any 

 microscopic observer. 



BiBL. Johnston, Brit. Sponges, Sfc; 

 Grant, Edinb. Neiv Phil. Mag. 1827 ; Hogg, 

 Ann. Nat. Hist. 1841. viii. 3, and 1851. vii. 

 190; Bowerbank, Trans. Micr. Soc. 1840. 

 i.; Carter, Ann. Nat. Hist. 1848. i. 303, and 

 1849. iv. 81 ; Dobie, Ann. Nat. Hist. 1852. 



X.317. 



SPONGILLA, Lam.— A genus of fresh- 

 water sponges. 



Two British species, S. fluviatilis and 

 S. lacustris. 



Found attached to stones, old wood-work, 

 &c. in still or slowly running waters ; green 

 or grey. 



See Spongi^. 



BiBL. Johnston, Brit. Sponges, 149, and 

 the Bibl. therein. 



SPONGIOLES.— Many works on vege- 

 table physiology still retain the old error 

 that the extremities of roots are devoid of 

 epidermis, and that the tissue then presents 

 an open spongy character, whence the name 



