1874.] Anatomy and Habits of the Genus Phroiiima. 157 



carrying the process a little further than it has perhaps yet been traced 

 by him : 



In lat. 21 0' S. and long. 17 45' W. off the island of Ono, Fiji 

 Group, apparently the same species of Plironima as that above described 

 was taken in the towing-net, but with the addition of a numerous pro- 

 geny of young in a large gelatinous but tough nidaniental case. This 

 interesting nest was shaped like a barrel, but with both ends open, and 

 the external surface was somewhat tuberculated and uneven. The wall 

 of the tube presented numerous round and puckered openings, observing 

 no very definite arrangement, but through which entering currents were 

 observed to pass. These openings generally, though not invariably, 

 pierced the tuberculations. 



An external membrane, with an internal lining, were distinctly visible, 

 both seeming to be continuous at the rims of the tube. The space between 

 these layers was filled up with a pulpy substance, in which scattered 

 nucleiforni bodies were detected with a higher power of the microscope. 



I have been particular in the description of the case, as some far- 

 fetched guesses were made as to its real nature. The cutting, piercing, 

 and tearing implements of Phronima would very soon alter and reduce a 

 bell-shaped Medusa, aSalpian, or a Pyrosoma tube to the required pattern ; 

 for there is usually a great uniformity in the character and. appearance 

 of this case. 



" With regard to Phronima" says Mr. Spence Bate*, " our knowledge 

 is small : its habit is that of an inhabitant of the gill-cavities of some one 

 or more species of Medina ; but in the Collection of the British Museum, 

 entrusted to my care for examination, is a very curious case that was 

 sent home from Naples by S. P. Pratt, Esq., as being the one in which the 

 animal was taken. The structure is thick, fleshy, semitransparent, and 

 studded over the surface and round the orifices one of which is smaller 

 than the other with numerous white excrescences. Examination with 

 the microscope shows the substance to be pervaded by bundles of fibres ; 

 each fasciculus is twisted together near its centre ; these, some of them 

 being larger than others, star the structure thickly, and still more plenti- 

 fully where the white excrescences appear." 



However problematical the nature of the case, that its use is for nidi- 

 fication there can be no further doubt. 



Though I. have already given figures of the specimen above noticed to 

 my friend Major Holland, E.M.L.I., for a paper 011 Phronima, published 

 in ' Science Gossip ' (April 1869), I trust that allusion to it here may not 

 be out of place. 



In a subsequent commission on the North- American and West-Indian 



Station in H.M.S. ' Icarus,' I have frequently captured " Phronima in 



its bag," as my messmates would say. In order to bring the swimmerets 



into full play, the animal protrudes its body tail foremost from the case, 



* Annals and Magazine of Natural History (Third Series), March 1858. 



