THE GONOPHORES OF DISTICHOPORA AND ALLOPORA. 189 



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 

 spermariura 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 coralliun, and lie at such a distance from the 

 surface that there is no trace of their existence externally. I 

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

 cannot say for certain whether Allopora is hermaphrodite 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 gonophores, 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 frag- 

 ments 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- 

 tichopora in every detail of structure except one, and that 

 is that the endoderm of the base is produced into the 

 substance of the spermarium as a club-shaped spadix or 

 manubrium (fig. 20, Spa.). 



