ON THE DEVELOPMENT OF TUBULIPOEA. 95 



from T. flabellaris, Fabr., are given below, under the ac- 

 count of that species. 



The ooeciostome of T. phalangea is shown in figs. 5, 6. 

 The convex upper surface is really the outer part of the wall 

 of the tube, which has the form of a fl, one limb of which 

 rises vertically from the roof of the ovicell, the other being 

 shortened and opening downwards. It results from this 

 arrangement that it is quite impossible to see the adult ooecio- 

 pore in the great majority of cases without breaking off the 

 series of zooecia which bears the tube, and turning it over until 

 the ooeciopore becomes visible. It is then seen to have the 

 form shown in fig. 6, being conspicuously smaller than that of 

 T. liliacea. The diameter of the ooeciopore varied from 110 

 to 135 f.1 in five specimens measured (average 118 fi), the 

 widest part of the entire tube varying from 110 to 180 fx 

 (average 139 fx) in the same specimens. The ooeciostome may 

 be quite symmetrical, or it may be distorted so that the ooecio- 

 pore looks obliquely downwards. When the ooeciostome is 

 typically developed (as in the great majority of cases), it differs 

 to a striking extent from that of any other species described in 

 this paper. 



In its typically developed form this species is distinguish- 

 able by its very long and slender zooecia, the ends of which 

 are more commonly dissociated from their neighbours (and 

 are therefore completely cylindrical) than in T. plumosa, 

 with which it commonly occurs. The character of the oldest 

 zooecia is of some value in distinguishing the species. While 

 T. plumosa is usually depressed in the oldest part of the 

 colony, this species has rather the opposite tendency, and the 

 primary zooecium usually grows upwards at a considerable 

 angle from the plane of support, the interval being occupied 

 by the proximal ends of the next zooecia. 



The general characters are well described by Couch (5, pp. 

 106, 107), though his fig. 7, pi. xix (wrongly given as fig. 8 

 in the text), is excessively bad. H. Milne Edwards (29, pi. xii, 

 figs. 1, 16, &c.) gives excellent figures of this species, accom- 

 panied by some anatomical details (pp. 323, &c.), under the 



