188 Mr. S. F. Harmer. Preliminary Note [Dec. 13, 



III. "Preliminary Note on Embryonic Fission in Lichenopora" 

 By SIDNEY F. HARMER, M.A., Fellow of King's College, 

 Cambridge, Superintendent of the University Museum of 

 Zoology. Communicated by A. SEDGWICK, F.R.S. Received 

 November 3, 1894. 



I have shown on a previous occasion* that the primary embryo of 

 Crisia gives rise to numerous larvae by a constantly repeated process 

 of embryonic fission, and I have suggested the probability that this 

 method of development will be found to be characteristic of Cyclo- 

 stomatous Polyzoa in general. Observations recently made on Licheno- 

 pora verrucaria, Fabr., obtained on the coast of Norway,f have enabled 

 me to prove the occurrence of embryonic fission in a second genus of 

 Cyclostomata, although the details of the development are remark- 

 ably different from those of Crisia. 



The colonies of Lichenopora verrucaria occur in great numbers on 

 fronds of Laminaria saccharina, growing just beneath low-watermark. 

 The colony is regularly plano-convex, with a diameter, in the full- 

 grown condition, of about 5 mm. ; and it is attached by its flat sur- 

 face to the sea-weed. Embryonic development commences with the 

 beginning of the formation of the colony, and the earliest stages 

 can only be followed by examining the initial stages of the colony 

 itself. 



The growth of the young colony closely resembles that of Tubu- 

 lipora flabellaris, Fabr., as described by Barrois.^ The colony origi- 

 nates from a circular disc, which, as Barrois has shown, results from 

 the calcification of the outer part of the body -wall of the larva after 

 its fixation. This disc is continued into the primary zocecium, which 

 buds off simultaneously, on its side turned towards the sea-weed, 

 two new zocecia, more or less parallel with itself. The first brood of 

 embryos is normally developed from the egg formed in one of these 

 two zooecia, although the egg is in some colonies formed in a younger 

 zocecium. 



The colony continues to grow in the form of a compressed funnel, 

 which at first lies on one of its flattened sides. By further growth, 

 the mouth of the funnel soon curves round so as to look directly 

 away from the sea-weed, its rim meanwhile extending in a plane 

 parallel to the surface of attachment, so as to overlap and finally 

 cover the disc from which the colony originated. The adult colony may 



* ' Quart. Journ. Mic. Sci.,' vol. 34, 18P3, p. 199. 



f For a part of this material I am indebted to the kindness of Dr. Brunchorst 

 and Dr. Nordgaard, of the Bergen Museum. 



% ' Kecherches sur 1'Embryologie des Bryozoaires,' 4to., Lille, 1877, pi. 4. 



