RHIZOPHYSA. 91 



I sought carefully for reproductive organs, but the only trace of them to be discovered 

 was two bunches of small, oval bodies, situated at the base of and between, two of the 

 polypites. These were oval, double-walled diverticula of the ccenosarc, with a ciliated 

 internal cavity, and about ,4th of an inch in length. Their ectoderm contained a few 

 thread-cells. 



I took a single specimen of this species in the Indian Ocean on the 2d of January, 1849. 



It was in this animal, as I have stated above, that I saw the air spontaneously expelled 

 from the orifice of the pneumatocyst. 



The only account of any species of BUzophysa which suffices the wants of the modern 

 naturalist is the excellent description of H. filiformis by Gegenbaur, in the ' Beitriige,' 

 to which I have so often had occasion to refer. This animal attains a foot and a quarter 

 in length, but has about the same sized pneumatophore and general thickness as that which 

 I have just described. 



In Gegenbaur's description of the structure of the pneumatophore, the facts agree pretty 

 closely with those which I have observed, but his interpretation of them is different. He seems, 

 in fact, to regard the layer of endoderm, reflected over the outer wall of the pneumatocyst, 

 as the whole wall of the pneumatophore, and hence he imagines that the apex of the 

 pneumatocyst is, at the superior pore, naked. The ciliated, cellular processes are described 

 just as I saw them. I did not observe the layers of small, round, yellowish cells which 

 he describes between the endoderm and the air-sac, whose presence, however, is extremely 

 interesting when we consider the position of the liver in Velella. 



Gegenbaur having supposed the reflected endoderm to be the ectoderm, naturally denies 

 that the apical pore can have any communication with the interior of the air-sac ; but 

 its real connexions are in favour of such a communication, and, as I have stated, I 

 distinctly saw air-bubbles escape from it. 



The young polypite is at first, according to Gegenbaur, a simple process of the wall 

 of the ccenosarc, whose cavity at first freely communicates with that of the latter. 

 The rudiment of the tentacle buds forth from the base of the polypite as this budded from 

 the ccenosarc ; and at the same time a process arises just in front of this rudiment, and 

 gradually reduces the communicating passage to a narrow canal, which can be completely 

 shut by muscular contraction. Eventually, the polypite opens at its apex, becomes 

 functionally active, and villi appear on its inner surface. 



Thus far Gegenbaur's observations agree so closely with my own that I can see no 

 ground for supposing that we examined different species, but, in his account of the tentacles, 

 he describes structures which, I think, I could hardly have overlooked, though, as I examined 

 but one specimen, I may have done so; or, perhaps, they were not developed in the tentacles 

 I examined. They consist, he states, of a stem with secondary branches, whose buds 

 are closely aggregated at the root of the stem. At the end of each branch are small, 

 mostly greenish capitula, which, when microscopically examined, appear as prehensile organs 

 (fang-organe) of a structure quite different from what obtains in other "polypi nechalei." 

 Their forms are various, but they may be reduced to the different states of three typical forms. 



In the first, the end of the branch is somewhat dilated and divided into three lobes, each 

 of which is beset with large thread-cells. 



