Pond-Life. 7 



Proceeding from the Morland ponds, there is a large pond 

 close to the railway, about midway between Woodside and 

 Elmer's End ; this contains a great many of the commoner 

 forms, but I have never succeeded in taking anything rare here ; 

 Ihere are plenty of rotifers, such as Rotifer vulgaris, Pterodina 

 ■patina, Philodina, and sometimes Brachionus ; the last named — on 

 account of its large size, well- developed gizzard, and strong 

 ciliary croAvn — is one of the best, as well as the easiest, of all the 

 rotifers for structural examination, Gosse, in his ' Evenings at 

 the Microscope,' devotes two or three pages to this particular 

 species. The scarlet water-mites are also tolerably abundant 

 here, as is also, at the present time, Melicerta ringens on the 

 water crowfoot. The tanks on the side-table represent a single 

 gathering from this pond. 



The only locality in our neighbourhood where the rare Hydra 

 fusca may be taken in any numbers, so far as I know, is the 

 Eiver Eavensbourne, between Elmer's End and Beckenham. It 

 is well worth looking for, being by far the most interesting of 

 the genus, both on account of its elegant shape and the length 

 of its tentacles when fully developed. I have several times met 

 with specimens an inch and a half in length, measured when the 

 hydra was perfectly quiet and undisturbed.* Its favourite 

 position in confinement is at the bottom of the aquarium, perched 

 on the top of a stone, the body erect and stretched to its utmost 

 extent, with the tentacles drooping gracefully round it. When, 

 as is sometimes the case, the specimen has four or five young 

 ones attached to it, the fishing-ground of the family covers 

 a large area. Of course, when the tentacles are extended to this 

 great length they become very much attenuated, so much so that 

 it is almost impossible to trace them to their extreme points ; but 

 this very attenuation is of advantage to the microscopist, for it 

 enables him to see with distinctness the stinging organs coiled 

 up in their cells, the skin covering them being so tightly 

 stretched as to be quite transparent. I have noticed in the 

 tentacles of this hydra what I think proves that the tentacles 

 are hollow, and contain water, and that is the presence of small 

 Infusoria. I have frequently, when using a high power, seen 

 them swimming about, and very amusing it is to watch them 

 shot backwards and forwards by the motion of the water in the 

 tentacles as these contract and expand ; and I think, although 

 not quite certain on this point, that the expansion and con- 

 traction of the tentacle is due as much to the injection or 

 ejection of water as it is to muscular action. 



For the collection of Ehizopods, the bed of Sphagnum on 



' Carpenter says tlie tentacles reach the length of 7 or 8 inches ; I have 

 never seen them anything like this length. 



