ON THE DEVELOPMENT OF TUBULIPORA. 149 



the " suspensor," constituted by the inner cells between the 

 brown body and the embryo, is probably represented in Tubu- 

 lipora by the nutritive tissue. 



The comparison Avith Crisia is less easy, but the main 

 difference — the absence in the ovicell of that genus of a 

 functional polypide degenerating to a brown body — has been 

 already commented on. 



Fig. 15 of pi. xxiv (15) shows a young ovicell with a bud 

 consisting of vestibule (distally), '" tentacle-sheath," and thick 

 proximal portion, corresponding with the alimentary canal and 

 tentacles of an ordinary polypide. Fig. 1 of the same paper is 

 probably younger, the part there marked "tentacle-sheath" 

 being more probably the vestibule, which is developed in 

 Cyclostomes before the tentacle-sheath. Fig. Sis considerably 

 later, and its *' tentacle-sheath " corresponds with the similarly 

 marked space in the later stages ; this is quite evident from 

 the fact that a vestibule like that of fig. 3 is present in the 

 ovicell which fig. 2 represents. Although fig. 2 is a good deal 

 later than fig. 1, it will be noticed that its egg is in much the 

 same state. The later ovicells formed a perfectly uninterrupted 

 series. It thus appears to me to be sufficiently established 

 that the vesicular bud of the ovicell of Crisia (15, fig. 1) gives 

 rise to the " follicle " (figs. 3, 5, 6) of later stages. If this is 

 the case, the cavity into which the follicle projects may be 

 really the tentacle-sheath, which would, on this hypothesis, be 

 much more developed than in Tubulipora. It seems to me 

 more probable, however, that the cavity of the embryophore 

 of Tubulipora is identical with the cavity of the "tentacle- 

 sheath " of Crisia, as is indicated by a comparison of fig. 25 

 of the present paper with fig. 8 of my former paper (15). The 

 apparent difference in the early stages is probably due to the 

 fact that the development of the so-called "tentacle-sheath " 

 of Crisia was not observed. 



The junction of the vestibule and embryophore in the ovicell 

 of Crisia (15, fig. 8) is marked by a thickening, which is bv 

 no means unlike the junction between the vestibule and the 

 embryophore in Tubulipora. I can hardly doubt, therefore, 



