THE GONOPHORES OB' DISTICHOPORA AND ALLOPORA. 193 



During the early stages of development the trophodisc 

 rapidly atrophies, and by the time a layer of columnar epi- 

 blast-cells has formed round the embryo no recognisable trace 

 of it can be seen (figs. 22 and 25). 



In the meantime young eggs are migrating from the sub- 

 jacent canals to the base of the ampulla, and in many cases 

 before the larva has escaped a new egg, borne by a new 

 trophodisc, occupies a considerable space in the same ampulla 

 (fig. 25). 



The young eggs (fig. 22, ov.) are frequently seen quite 

 deeply situated in the canal system ; those that are nearer 

 to the ampullae are larger in size and amoeboid in shape. 

 As soon as they reach the ampulla they show very minute 

 yolk-granules, which increase in size with the growth of the 

 egg and the development of the trophodisc. 



The female gonophores of a few species of Stylasteridae have 

 already been figured and described by Moseley (10). 



In Pliobothrus symmetricus "the gonophores are con- 

 tained in ampullae which are often sunk deep in the coenosteum. 

 .... The ova are solitary, one only being developed in each 

 growing ampulla. Each ovum is developed within the cup of 

 a cup-shaped spadix," i.e. trophodisc. " As the ovum advances 

 in development and increases in size the spadix enlarges with it. 

 Subsequently, however, in later stages, the spadix appears not 

 to increase further, and when in relation with a nearly fully 

 developed planula appears proportionately small." 



In Errina labiata "the female gonophores are closely 

 similar in structure to those of Pliobothrus symmetricus; 

 but there is this great difference, that whilst in Pliobothrus 

 the ampullae and their contained ova and planulae remain until 

 maturity immersed in the ccenosteum beneath its surface, in 

 Errina the ampullae project more and more above the surface 

 as development proceeds. 



"The spadix in Errina labiata is at first cup-shaped, the 

 walls of the cup being composed of a very thick layer of endo- 

 derm. The cavity of the cup is directed towards the surface of 

 the coral, and within it rests the single large ovum with its 



