190 SYDNEY J. HICKSON. 



The spermarium is covered by a double sheath of very thin 

 ectoderm and endoderm, and the seminal duct is produced in 

 the same way that it is in Distichopora. When the sper- 

 marium is ripe the seminal duct perforates the superjacent 

 structures, and serves as the duct for the spermatozoa to 

 escape to the exterior. As the gonophores of AlJopora are 

 situated much more deeply than they are in Distichopora, 

 the seminal ducts are considerably longer. 



As a rule, only one gonophore is seen in each ampulla of 

 AUopora, but occasionally two (fig. 19, gonophore 2), and 

 very rarely three, in different stages of development may be 

 seen. 



Lastly, it must be observed that the fully developed male 

 gonophores of AUopora are much larger than those of Dis- 

 tichopora. 



From a largce number of measurements I have obtained the 



following average measurements : 



Longest diameter of male gonophores of AUopora . 0"38 mm. 

 „ „ „ Distichopora 0"19 „ 



The male gonophores of a few species of Stylasteridse have 

 been described by Moseley (10). 



In Sporadopora dichotoma the specimens were all males. 

 " They are ovoid bodies with the long axes directed at right 

 angles to the surface of the coral. Sometimes only one such 

 body is present in an ampulla ; sometimes two or three. The 

 outer extremities of the gonophores are sometimes drawn 

 out into a short tail-like prolongation." This structure pro- 

 bably corresponds with the seminal duct of AUopora and 

 Distichopora. "There is a cylindrical spadix in the centre. 

 The bases of the gonophores are continuous with large canals 

 of the coenosarcal meshwork, the endoderm of the spadix being 

 continuous with that of these canals." 



In Pliobothrus symmetricus the male gonophores are 

 sacs containing a number of small ovoid bodies, which contain 

 spermatozoa, or sperm-cells, in various stages of development. 

 The exact structure of these smaller bodies and their relations 

 to the endoderm were not determined. 



