ON THE DEVELOPMENT OF TDBULIPORA. 131 



pointing to the degeneration of a polypide at a stage when the 

 embryo consists of about 2 — 4 blastomeres, at first enclosed 

 in the original follicle of the egg, the follicle ceasing to be 

 distinct in the later stages. In two of these cases additional 

 evidence that the degeneration was a normal stage in the 

 development of the ovicell was afforded by the fact that it was 

 in the position relatively to an obvious ovicell which it might 

 have been expected to occupy, from the fact that two ovicells 

 are so commonly found in young colonies. Fig. 12 shows the 

 beginning of the degeneration of the fertile polypide. The 

 section cuts the edge of the mass of tentacles, which in the 

 next few sections are obscurely defined^ showing that degenera- 

 tion is taking place. Parts of the alimentary canal are visible 

 in the section figured. The nuclei of the follicle are not so 

 regularly arranged as in the case of unfertilised eggs. The 

 embryo has two cells, which lie in a distinct follicle-cavity. 



Fig. 13 (T. phalangea) shows a later stage, drawn with a 

 higher power. The brown body, which is only indicated in the 

 figure, still shows some traces of the parts of the alimentary 

 canal of tiie fertile polypide, whereas a fully formed fertile brown 

 body shows no such traces, and consists of a granular pigmented 

 mass, containing a few nuclei. The embryo certainly possesses 

 three blastomeres, while the elongated nuclei of two of the cells 

 of the egg-follicle are clearly seen. The follicle contains a 

 minute deeply stained body, which is almost certainly the 

 remains of a spermatozoon. 



The terminal membrane of the fertile zocEcium plays an 

 important part in the development of the future ovicell. The 

 evidence afforded by this and the next stage appears to be 

 that the orifice of the vestibule closes at the degeneration of 

 the polypide, and that the terminal membrane retires some 

 little distance within the calcareous orifice. It is, however, 

 difficult to be certain how far this regression is normal, and 

 how far it is an artefact. 



[Stage C (functional polypide -fembryophore) of Licheno- 

 pora is not represented in the development of Tubulipora.l 



