No. 3-] DEVELOPMEXT OF MARIXE SPOXGES. 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 upper end. 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. PI. XIX, Fig. 63, represents a section cut from a 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. cf. c. in Fig. 63. Of these, 

 three appear in the section. A fourth unites at this level with 

 the central canal, c. cf. 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 

 PI. XX, Fig. 67 c. 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 



