6 Spon g. 
XVII. SPONGIiE. 
IT.— BIOLOGY. 
1 . MORPHOLOGY and PHYSIOLOGY. 
a. General (12, 15, 17, 18, 83, 35). 
Haeckel (18) draws attention to the importance of Individuality in 
Sponges and complains that it is not taken sufficiently into account by 
Spongiologists. He considers the simple Ascon ( Olynthus ) and the 
ciliated chamber of all higher Sponges ( Heteroccela and Silicea ) to be an 
individual or “ person,” and believes that all higher Sponges are colonies 
like the colony-forming Corals, the ciliated Sponge chamber being 
homologous to a Polyp of a Coral colony. All the parts of Sponges 
which are not ciliated chambers are to be considered as Coenenchym. 
Minciiin (35) considers the interstitial layer as a sort of ectodermal 
subepithelium and not as a mesoderm ; the Sponges are accordingly two- 
layered (and not three-layered) organisms. 
b. Canal System (18, 44, 55) 
Weltner (55) has carefully investigated Ephydatia JluviatiliSj and finds 
that the subdermal cavities are very large in this species. The inhalent 
canals proper are so extensive, that usually only thin trabecula) of sponge 
tissue separate them. The ciliated chambers are spherical, 0*028 — 0.05 in 
diameter, and provided with 3-5 afferent pores. Oscular chimneys are 
often present. Large specimens always have more than one osculum. 
F. E. Schulze (44) proves the dip ] odal nature of the ciliated chambers 
in Corticium candelabrum , Choudrilla Jiucula, and Oscarella lobularis, by 
means of photographs, which clearly show both the afferent and the 
efferent chamber-canals. These photographs demonstrate the incorrect- 
ness of Topsent’s statements, according to which these Sponges have 
no afferent chamber- canals. 
c. Skeleton (18, 43, 51, 55). 
Hasckel (18) distinguishes the following six kinds of siliceous spicules: 
“ Monaxillen ” = Monaxons; “ Trigonillen 55 = Triactins; “ Tetraxillen ” 
= Tetraxons ; “ Hexactillen ” == Triaxons ; “ Pollaxillen” = Polyaxons; 
and “ Anomaxillen ” = Desms ; and the following three kinds of cal- 
careous spicules: “ Trigonillen ” = Triactins; “ Tetraxillen =. Te- 
tractins ; and “ Monaxillen ” = Monaxons. He also discusses the various 
evolutionary possibilities of deriving these spicule forms from each other. 
F. E. Schulze (43) has established the following new names for 
triaxon spicules : Calicocom y Hexaster, the primary rays of which termin- 
ate each in a cup-shaped extension, cylindrical, smooth, secondary 
(branch-) rays arise from the cup-margin. Codonhexaster , Discohexaster, 
the terminal discs of which are strongly recurved, semispherical with 
toothed margin, the teeth are long and lie parallel to that secondary ray 
to which the disc belongs. Drepanocom , a Floricom-like Hexaster, the 
secondary rays of which are, however, smooth, sharp-pointed, and 
terminally recurved like a scythe. Grapkiocom } for Graphiohexaster. 
It has been found that certain spicules of Aphrocallistes and other 
Hexactinellids, previously described as Discohexasters, or Oxyhexasters, 
bear on the termini of their secondary rays slender, vertically disposed 
spines curved backwards like claws, for which spicules now the name 
Onychaster is established. Oxystauractin , a Stauractin with pointed rays. 
Siymatocom } like the Drepanocom , but with upstanding, not recurved 
