THE GONOPHORES OF DISTICHOPOEA AND ALLOPOEA. 383 



spermarium (fig. 16). At the peripheral pole of buds that 

 are about half-way developed there is a thickening of the two 

 sheaths of the gonophores, cell outlines are well marked, and 

 the cells are nucleated (figs. 14 and 16). In this way the first 

 rudiment of the seminal duct is formed. The two layers are 

 from their first appearance quite distinct from one another, 

 and there is never any indication that the two cell layers 

 are formed by a splitting of the ectoderm. Just before the 

 spermarium becomes mature the ectoderm, and subsequently 

 the endoderm, are folded to form a conical cap, and this 

 subsequently pushes through the superficial covering of the 

 gonangium to form the seminal duct to the exterior (fig. 18). 



Meanwhile, changes have taken place in the endoderm at 

 the base, i. e. on the axial side of the bud. In the early 

 stages of the bud there is a wide lumen in the endoderm, the 

 cells are cubical in shape, and their outlines well marked ; in 

 the later stages the lumen becomes obliterated, the cells lose 

 their distinct outline, and the endoderm degenerates into an 

 irregular mass of tissue, with scattered nuclei (figs. 13, 14, 

 15, 16). 



2. In Allopora (fig. 19) the male gonophores are scattered 

 irregularly in the corallum, and lie at such a distance from 

 the surface that there is no trace of their existence exter- 

 nally. I have been able to find them only in the old thick 

 branches. I cannot say for certain whether Allopora is her- 

 maphrodite or dioecious. The specimens at my disposal 

 consisted of a number of fragments in a bottle, and I found 

 on the smaller and younger branches numerous female gono- 

 phores, and on the thicker and older branches numerous male 

 gonophores ; but I have not found both sexes on the 

 same branches. I have no information whether the older 

 and younger branches in the bottle are fragments of the same 

 colony. If Allopora is not dioecious, then it is probably 

 protogynous, like Millepora, the female sexual cells being 

 formed first in the younger parts of the colony, and the male 

 sexual cells later in the older parts. 



The male gonophores of Allopora resemble those of Dis- 



