No. 3.] DEVELOPMENT OF MARINE SPONGES. 323 
the oscular papillae, or in the upper part of young sponges of 
a conical shape, a few inches high. In both the oscular papilla 
and the upper part of the young sponge, the furrows or super- 
ficial gelatinous tracts run with comparative directness straight 
towards the upperend. An indistinct radial symmetry is thus 
given the papilla, which appears more pronounced after the 
efferent canals are studied. For it nearly always happens that 
the papilla has in its axis some one canal larger than the rest, 
and each superficial gelatinous tract has likewise, as a rule, one 
large efferent canal, so that near its upper end the efferent 
system of the papilla consists of a central canal, round which 
are disposed several superficial canals, all either opening by a 
single osculum or by two or three separate but closely adjoining 
oscula. Pl. XIX, Fig. 63, represents a section cut froma young 
sponge of a conical shape and some five inches high. At the 
apex of the sponge was a single osculum, and the section drawn 
was cut a short distance below it. In this region the superficial 
gelatinous tracts contain no subdermal cavities. All that each 
contains is a single efferent canal running parallel to the 
surface and towards the apex, sup. ef. c. in Fig. 63. Of these, 
three appear in the section. A fourth unites at this level with 
the central canal, c. ef. c. Lower down the number of super- 
ficial canals increases, but they no longer run in the same 
direction, pursuing, on the contrary, the irregular meandering 
course characteristic of the general surface. The canals shown 
in Fig. 63 all open by a common orifice, which I have spoken 
of as the osculum, at the apex of the sponge. 
The flagellated chambers are spheroidal, and the mesoderm 
of the spongy tracts is comparatively abundant, consisting of 
rounded or branched amoeboid and spindle-shaped cells. The 
gelatinous tissue is composed of a network of cells with an 
abundance of watery jelly in the interstices. The cells as a 
rule have small bodies and several long slender processes, 
Fig. 64. 
The tylotes found in Tedania B. all have nicked heads as in 
Pl. XX, Fig. 67¢. This seems to be a common variation in 
the species of Tedania. Oscar Schmidt in speaking of the 
Atlantic Tedanias, says : ‘Die meisten dieser Tedanien besitzen 
