TUBULIPORA HYALINA. 487 



Colonies forming small patches of about the diameter of a 

 pea. 



HABITAT. On Fucus palmatus. 

 LOCALITY. Polperro, rare (Couch). 



Possibly founded on young specimens of some species of 

 Lichenopora. 



NOTE ON THE ORIGIN OF THE CYCLOSTOME COLONY. 



ACCORDING to Barrois*, the larva of Tubulipora, soon after 

 fixation, appears as a discoid body (woodcut, fig. 26, pd), 

 which is inclosed by an obscurely cellular endocyst, around 

 which a calcareous ectocyst is developed, forming an opaque 

 ring round the whole structure (fig. 26, ect) . The centre 

 of the discoid cell is occupied by a pyriform body ; and 

 between this and the inner wall (cudocyst) lies a soft and 

 transparent mass of fatty globules. The central body is 

 gradually moulded into a polypide (fig. 26, pot) : from 

 the endocyst a round swelling originates over the tentacular 

 region of the polypide, which is _,. ^ 



developed into a calcareous tube 

 (fig. 26, T). The tentacles are 

 soon partially included in this 

 tube, which ultimately becomes 

 the true cell and the perma- 

 nent home of the polypide. The 

 original disk is converted into 

 a mere organ of attachment, and 

 is separated by a diaphragm from 

 the tubular cell. In this condition 

 it commonly occurs attached to 

 the adult Cyclostoraatous colony. 



* ' fiech. iur IVmbryologic dee Bryozoftiren,' pp. 70. 71 . 



