THE LOWER FORMS OF LIFE. 89 



the muscles of the chest, which were stiff, as in rheumatism, causing 

 painful dyspnoea. 



In the specimen of Physalis caught off the Isle of Wight there 

 was a fish entangled in the tentacula ; and Mr. Bennett had the 

 opportunity of watching in his, taken under similar circumstances, 

 the progress of absorption of the digesting fish. As it shows all 

 the principal parts very well, I have figured the small variety called 

 by Eschscholtz P. utriculus, and which is drawn from life, and very 

 minutely described by Professor Huxley in his monograph of the 

 ''Oceanic Hydrozoa." When the long tentacles (b) have come in 

 contact and seized and benumbed say a small fish they shorten 

 themselves by assuming a corkscrew form, and the prey is then 

 brought up to the polypites, which are seen with their open mouths 

 at c, and which are erroneously called small tentacles by those 

 who do not correctly follow the morphology of the Hydrozoa. The 

 prey being brought within convenient distance, each polypite applies 

 his sucker-like mouth, and the feast begins. Mr. Bennett describes 

 the passage of particles of the fish, as seen through the transparent 

 tissues along the absorbents. In reality he saw them passing into 

 the stomach of the polypites, just as he might witness the same 

 process in the fresh- water Hydra. 



Like the Calycophoridse, many of the Physophoridae have swim- 

 ming cups ; but, in addition, they possess a remarkable organ called 

 a pneumatophore, which is, in fact, a chamber filled with air, by 

 which they float permanently in the water. Mark here the design 

 shown in the formation of the last two orders of Zoophytes. The 

 cup-bearers move voluntarily through the water, and are provided 

 with an apparatus for that purpose. The air-bag would be to them 

 an incumbrance ; but, as the bladder-bearers have no such organs 

 of locomotion, they are provided with an apparatus which, being 

 filled with a fluid lighter than water, keeps them permanently afloat. 

 Now, this pneumatophore is generally placed at the proximal end or 

 apex of the Physophorid ; and, as it cannot always be seen in draw- 

 ings of the animals, I have given a diagram from Professor Green's 

 excellent manual of the Coslenterata, which will illustrate the position 

 of this organ in all the genera, and at the same time show how the 

 order wt are now dealing with differs from the last (Fig. 117, p. 91). 

 This pneumatophore is diagnostic of the Physophoridae. In the 

 " Man-of-war " it constitutes the greater part of the larger bladder- 

 like coenosarc (a, Fig. Ill, p. 90). It contains within it another bag, 

 called by Huxley a pneumatocyst, which has an opening communi- 

 cating with the external air. There are two series of tentacles, the 

 long dependent (b), and the shorter ones (d). At the base of each 

 tentacle there is a fleshy ccecal bag (e), which is covered externally, 



