:)G4 CUMINGS and galloway MORPHOLOGY OF TREPOSTOMATA 



beyond question. In addition, we have occasionally seen a whole battery 

 of spines of unnsually large size surrounding the hole of a parasitic 

 boring worm that had penetrated the zoarium. There are, however, 

 many different kinds of acanthopores, and it is not likely that they all 

 had the same function. The type described abo\e is common in the 

 Heterotrypidffi, in some species of Tloinotrypa, in HoniotnjpeUa, Perono- 

 pora, etcetera. On the other hand, the minute acanthopores with ill- 

 defined lumen, so often seen in Homotrypa and other genera, may have 

 supported an exsert process of a very different sort. 



Merlia Normani Kirkpatrick 



After the senior author's paper on the development of the Monticu- 

 liporoids (8) was distributed, Dr. W. D. Lang, of the British Museum, 

 called our attention to several notes that had been published in Nature 

 and the Proceedings of the Eoyal Society by Doctor Kirkpatrick, of the 

 Museum, in regard to a peculiar recent sponge, having an auxiliary skele- 

 ton, externally greatly resembling the zoaria of certain Monticuliporoids 

 (16, 17). Doctor Kirkpatrick in these announcements states without 

 hesitation that, on the basis of the resemblances mentioned, Monticulipora 

 should be regarded as a sponge. In his elaborate paper on the morphol- 

 ogy of Media, Doctor Kirkpatrick (15) had taken a much more conserva- 

 tive view of the resemblances. 



Through the kindness of Doctor Lang and Doctor Kirkpatrick we 

 were able to obtain several specimens of Merlia, preserved in alcohol. 

 We have sectioned these and made a very careful study of the wall 

 structure, which is shown in tangential section in figure 41. A glance 

 will convince any one that there is not the slightest resemblance between 

 this structure and anything ever seen in the Trepostomata. In Media 

 the calcification evidently proceeds by spiculation from definite centers 

 {c, c). At the growing edges of colonies of Media the skeletal ele- 

 ments have not yet coalesced, and one sees here nothing but chains of 

 small erect pillars distinctly separated from each other. In later growth 

 these coalesce by the radial extension of their spicules or fibers. In 

 longitudinal sections of the walls these fibers are seen to arise vertically 

 from the substratum and turn ouUvard, like the straws in a sheaf of 

 wheat. This explains the appearance shown in the tangential section. 

 The central granular-appearing nucleus is where tlie fibers are cut trans- 

 versely, and the zone of radiating fibers surrounding the nucleus is where 

 the outward-turning fibers are cut more and more longitudinally. The 

 boundaries between adjacent sheaves of spicules are very sharp. The 



