V-' 



ON THE DEVELOPMENT OP TUBULIPORA. 93 



side of the branch) from the bifurcation preceding the ovicell; 

 whereas in another branch the ooeciostome is on the proximal 

 side of the eighth series of one side^ the ovicell itself beginning 

 immediately after the fifth series. 



The ovicells of this colony extend through a region of four 

 or five transverse series of zooecia on each side of the fertile 

 lobe. The shape of the ovicell is of course affected by the 

 strongly marked alternate arrangement of the series, and its 

 roof is thus a comparatively narrow, curvedly zigzag band, 

 running along the middle of the lobe, and giving off an inter- 

 serial lobe on the convex side of each bend. The ovicell may 

 thus be described as consisting of a regularly undulating axis, 

 with an alternately pinnate arrangement of simple lobes ex- 

 tending between the series of zooecia. The ends of the 

 branches are bifurcated, but the same ovicell extends into both 

 halves of the fork by division of its main axis. The same 

 arrangement is figured by Smitt (40, pi. iv, figs. 5 and 7) in 

 Idmonea atlantica. 



A great contrast to this Idmonea-like colony was afforded 

 by a fine specimen from the Liverpool district kindly lent to 

 me by Professor Herdmau. A narrow branch suddenly ex- 

 panded into a nearly semicircular fertile lobe, 6 mm. in trans- 

 verse diameter. The zooecia in this lobe had a. Tubulipora- 

 like arrangement, consisting of radial series, which showed a 

 distinct tendency to become frayed out into separate zooecia at 

 their upper borders. The ooeciostome had the typical form, 

 and other colonies from the same locality were in no way dif- 

 ferent from the more ordinary type of T. liliacea. 



I think there can be no doubt that the form of ooeciostome 

 which I have described is quite characteristic of this species. 

 Although I first noticed it in a number of specimens from the 

 Plymouth district, it is not a local peculiarity, since I have 

 found precisely the same form in the specimens which have 

 just been alluded to from Trondhjem and Liverpool, as well 

 as in a series of colonies from Hydroids dredged in St. 

 Andrews Bay (20 to 27 fathoms), kindly given to me by Pro- 

 fessor Mcintosh. The variations in the size of the ooeciopore 



