ON THE DEVELOPMENT OF TUBULIPORA. 107 



Mr. W. Thompson, wliose name I have adopted. The de- 

 scription and figures given by Johnston leave no doubt in my 

 mind that Thompson's T. plumosa is the form of which I 

 have given a diagnosis above. The flat central region of the 

 colony, which alone is developed in Johnston's figs. 5 and 6 

 (pi. xlvi), is eminently characteristic of the present species. 

 This form is indeed not invariably assumed by it, but is very 

 distinctive when it does occur. In this condition the zocecia 

 are often strongly ridged transversely, in the manner de- 

 scribed in Johnston's work, and the serial arrangement of the 

 zocecia is hardly apparent unless the colony is looked at from 

 its distal edge. The shortness of the tubes alluded to by 

 Johnston is of course due to the fact that they are im- 

 mature. • 



Specimens with this depressed central region are usually 

 easy to distinguish from T. phalange a, with which the species 

 is associated on red seaweeds. The radial ridges formed by 

 the more projecting zooecia are the commencements of the 

 series of zooecia. As the colony increases in diameter, the 

 freshly added parts of these projecting zooecia project more 

 and more, younger zooecia are developed connately with them 

 on their lower side, and the serial arrangement becomes as 

 strongly marked as in any other species of Tubulipora. 



T. plumosa is described by Hincks (18, p. 448, pi. Ix, 

 figs.Sand 3a) from immature specimens as T. fimbria, Lamk. 

 Fig. 3 of this author shows the beginning of an ovicell on 

 the right side, although the septa between the ovicell and 

 the contiguous zooecia are not all indicated. Mr. Hincks 

 expresses a doubt as to the identity of this species with 

 T. fimbria, Lamk., but accepts the name with some hesi- 

 tation on Smitt's authority. Smitt's T. fimbria is, however, 

 in my opinion, a different species, and it is here described as 

 T. aperta. The figure of T. "fimbria,^' given by Milne 

 Edwards (29, pi. xiv, fig. 2) from a specimen labelled by 

 Lamarck, does not specially resemble T. plumosa. 



The distinctive feature of T. plumosa is the ooeciostome 

 (fig. 1), which is a wide, funnel-shaped structure, looking up- 



