DROMALIA ALEXANDRI. 307 



lamellae, is exactly comparable to the corresponding dorsal zone flanked by the 

 bracts in Anthophysa. There is no evidence whatever that the appendages of 

 the aurophore in Dromalia ever develop into nectophores or cormidia. 



Furthermore the cormidia which lie immediately below the vacant zone 

 are all large, with well-developed gonophores, and there is no evidence except as 

 described later (p. 308) of the interpolation of newly developed ones among them. 

 I may point out, however, that the two or three muscle bands lying nearest 

 the vacant zone on either hand are considerably shorter than their neighbors, 

 a fact which, as I shall show (p. 315) has an important bearing on Haeckel's 

 figures of Rhodalia. But while no young appendages are found on the same 

 side of the corm as the aurophore, a photograph of the lateral aspect of the 

 corm (Plate 23, fig. 6) shows clearly that young cormidia and nectophores are 

 being formed at a point exactly opposite the aurophore, immediately below 

 the union of pneumatophore with nectosome. This fact is as evident on all the 

 specimens, as is the presence of the pneumatophore itself, and it is even more 

 clearly demonstrated in a radial section (Plate 24, figs. 4, 5). The details of 

 the zone of proliferation are best seen in a surface view of the face of the corm 

 opposite the aurophore (Plate 24, fig. 1, 3). Just below the pneumatophore, 

 and in the radius exactly opposite the aurophore, is a well-marked ridge, 

 the " blastocrene " of Hae'ckel, some 1-2 mm. long. This bears numerous very 

 young appendages on its outer edge. Below it is to be seen a single row of 

 young cormidia in successive stages of development. Close on either side of 

 the blastocrene lie the young nectophores. The youngest are next to it, and 

 immediately below the pneumatophore, the older ones successively farther apart 

 laterally as well as lower down (Plate 24, fig. 2, 3). In the photograph (Plate 

 24, fig. 3) four nectophores are to be seen, the two oldest already showing well- 

 developed muscular lamellae. In none of the specimens were any of the older 

 nectophores attached. But their growth is indicated by the successively increas- 

 ing length of their muscle bands at greater and greater distances laterally from 

 the blastocrene. Before passing on to the account of the older cormidia, I wish 

 to emphasize the important fact that nothing in the entire anatomy of Dromalia 

 is more certain, or more clearly and easily distinguishable, than that the auro- 

 phore and the zone of prohferation lie on opposite sides of the corm. For a 

 comparison of this statement wuth Haeckel's observations and the opposite 

 conclusions of Lens and Van Riemsdijk, see page 314. 



Arrangement of the cormidia on the siphosome. From the blastocrene to the 

 level where the nectosome joins the bulbular siphosome, the young cormidia lie 



