226 J. H. ASHWORTH. 



tentacles, the open mouth, the siphonoglyph, the goblet-cells in the 

 stoinodaeum, the dorsal mesenterial filaments, and the primitive genital 

 cells. A polyp which has reached this stage of development would 

 probably be quite capable of supporting itself, as, by means of its 

 siphonoglyph and dorsal mesenterial filaments, it would be able to 

 create the currents necessary for its nutrition and for keeping up the 

 circulation of liquid in the ccelenteron. 



In a polyp *95 mm. long (V. in table, p. 215) the first two pinnules 

 are distinguishable upon each tentacle. The stomodeeum is "6 mm. 

 long, and the siphonoglyph extends along the ventral side of the lower, 

 •34 mm. The lips of the stomodeeum are widely open below. Flagella- 

 bearing cells are much more numerous in this polyp than in any of the 

 young polyps previously described. They are fewer in number in the 

 upper part of the coelenteron than in the deeper portions. Their 

 flagella are still short, not exceding 30 fi in length (Fig. 36, G. F.). 



A polyp 1 mm. long (VI. in table) is seen in section in PI. 25, Fig. 8. 

 Its tentacles bear near the tip one pinnule on each side of the axis. 

 The stomodeeum is *74 mm. long, and exhibits a well-marked siphono- 

 glyph, bearing flagella in its lower half. The dorsal mesenterial 

 filaments are well developed, and extend in a sinuous course nearly 1 

 mm. down the coelenteron. The coelenteron extends 1*4 mm. into the 

 stem, curving so as to be parallel to the neighbouring ccelentera. Its 

 connections with the longitudinal and superficial canals may be seen 

 in the figure. The flagella of the endoderm cells attain 40 /u in length. 

 The distribution of spicules, nematocysts, and zooxanthellee is shown in 

 the figure. In such a polyp all the adult structures are differentiated. 

 In the growth of the polyp, from this point onwards to the full adult 

 size, there are few features which call for comment. The chief of these 

 are the formation of a greater number of pinnules on the tentacles ; 

 the elongation of the coelenteron outwards (as the free portion of 

 the polyp grows in length) and inwards into the mesogloea, where it 

 curves, so as to lie parallel to the neighbouring ccelentera (PI. 25, Fig. 

 8) ; the increase in number and size of the giant flagella on the endo 

 derm cells, and the development of sperm sacs on the mesenteries. 



