MORPHOLOGY AND DEVELOPMENT OF EUDENDRIUM. 



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(Fig. 3). This is produced by the active proliferation of the 

 ectoderm adjoining the egg. For a time the cells differ little 

 from those of the hydranth ectoderm. Soon the entoderm just 

 above the egg begins to form a blunt tube of columnar cells 

 opening into the enteric cavity. The end grows outward be- 

 tween egg and mesoglosa. Growth of the base aids in carrying 

 the egg out from the general surface of the hydranth (Fig. 4.) 

 Continued elongation brings the end of the 

 tube over the top of the egg and down the 

 outside where it divides sending a branch 

 inward and upward on either side to form 

 the coil. Viewed from the side the spadix 

 now looks like a spiral of one and a half 

 turns. Linear growth of the spadix is nearly 

 complete when the egg has one third of its 

 mature diameter. It stands out from the 

 surface at first, but in time becomes flattened 

 against the egg. 



The ectoderm undergoes a gradual change 

 to a thin tough sheath covered by a tenuous 

 perisarc. It passes over the spadix and else- 

 where is separated from the egg by the 

 mesoglcea only. Together with the base of 

 the spadix, it forms the stalk of the gono- 

 phore. 



While the spadix is developing the egg 

 rounds out into a sphere and rapidly en- 

 larges. Its increase in bulk is due to the 

 formation of large granules of deutoplasm. 



Weismann, 'Si 1 , describes a contraction and expansion of the 

 spadix in the living gonophore of Corync piisilla which he thinks 

 functions to move the nutritive fluid, used by the growing egg. 

 Variations in the diameter of spadix lumen of E. ramosnm sug- 

 gest that the same motion occurs in it. There can be no doubt 

 that the egg absorbs nourishment through the walls of the spadix, 

 as has been pointed out by others. Dr. Hargitt has suggested 

 that the flattening of the spadix is due to the absorption by the 

 egg of the contents of its cells. 



FIG. 2. 



