FLUSTRA. 13 



conspicuous in the Tubularia, and what is less obvious in the Sertularia, 

 has been hitherto discovered, whereby the simple enlargement of entire 

 specimens may be explained. 



Neither is the formation of the strong yellow marginal band of the 

 yellow stem explicit. It is not ascertained to be generated through the 

 medium of new cells, whence we should infer that it originates from some 

 deposit of the old. 



Under all these circumstances, however, though no connection or 

 communication between the cells of the Flustra be discovered, there is a 

 strong presumption of some imperceptible channel or medium traversing 

 the leaf, whereby portions with new hydra? are generated from the older 

 parts. 



Still it is difficult to explain the fact. More protracted observations, 

 under favourable circumstances, might afford a solution of these and other 

 questions, at present very obscure. 



Plate I. Flustra Carbasea. 



Plate II. Flustra Carbasea. 

 Fig. 1. Leaf of a specimen. 



2. Portion of a leaf. 



3. Portion of a leaf with cells and hydrse. 



4. Hydra quiescent in its cell. 



5. Hydra displayed — front. 



6. Corpuscula, free. 



7. Corpuscula free, more enlarged. 



8. Spots from the corpuscula become stationary. 



9. Spot with a nucleus and diffusing margin. 

 10 Hydra originating from the nucleus. 



11. The same more enlarged, shewing the position of the tentaoula. 



12. Nascent Flustra. 



13. Another. 

 14-19. Nascent Flustrae. 



20. Nascent Flustra, having generated a second hydra. 

 21-23. Nascent Flustra preserving the second hydra, after the first had de- 

 cayed. 



