188 Bibliographical Notices. 



hydra into perfect configuration, and the display of the organic 

 parts actually completed under the observer's eye. My notice having 

 been directed to a specimen, wherein, from the highest of three frills, 

 a dark green globular mass rose prominent as an acorn in the cup ; 

 in an hour it became somewhat clavate, while turned slightly aside, 

 still enlarging without any indications of tentacula. But in another 

 hour these organs became perceptible through a very delicate trans- 

 parent involucrum protecting the mass. The head had now pro- 

 truded almost entirely from the frill, and the extremities of the ten- 

 tacula separating, having improved the symmetry of the parts, they 

 were gradually and at length freely unfolded two hours afterwards 

 in their due proportions. The new head of the finest green was 

 perhaps the fourth which the twig sustaining it had borne in suc- 

 cession." (p. 165.) 



13. Thoa Beanii. Well figured and described, and its history 

 completed by the description of the animal and of its planule. 



14. Thoa muricata. The author has never observed " any visible 

 object " ever discharged from the muricated vesicles of this species, 

 though he has had many specimens at various seasons of the year, 

 and which were preserved with every possible care. He questions 

 whether the capsules are truly vesicles, or whether they are not rather 

 extraneous substances — the capsules of some of the Testacea. They 

 are certainly not the capsules of any bivalve, as suggested, but they 

 may be those of a zoophagous gasteropod. We incline, however, to 

 believe them integral parts of the zoophyte. 



15. Plumularia falcata. A beautiful history of the species. 



16. Plumularia pinnata. 



17. Plumularia} fascis. This is apparently a new species allied 

 to P. calharina. The magnified figures are scarcely sufficient. 



18. Sertularia argentea. The figures appear to us to represent 

 S. cupressina, but the author entertains doubts whether the two be 

 truly diff^erent, and his observations tend to prove that they are not 

 so. The species has two sorts of vesicles, a simple one resembling 

 a vase, and one " of compound formation, consisting of a hollow 

 pedestal, surmounted by a sphere about three times its diameter," 

 p. 192, The propagation is very minutely detailed. 



19. Antennularia antennina. 



20. Antennularia ramosa. The author has proved these to be 

 perfectly distinct. The first has a vesicle which produces " a single 

 yellow embryo " " so large that there seems no room for more. It 

 is evolved as a planula, surpassing the size of any that I have seen 

 issuing from a Sertularia, for it is nearly the twelfth of an inch in 

 length," p. 201. But the vesicles of A. ramosa contain many — from 

 twelve to thirty — corpuscules, and the planula is very minute, " not 

 exceeding the sixth part of the size of the single yellow planula " 

 of A. antennina. After some interesting observations, the author 

 concludes (1.) that A. antennina has " a single ruddy stalk ten inches 

 high, begirt by slender verticillate twigs, and bearing axillary ovate 

 vesicles, each containing a single j-ellow planule ;" (2.) that A. I'U' 

 mosa is " a greenish shrub, diverging into boughs and branches, clothed 



