266 



zooLoav 



they have gained an elongated, cyhndrical form. There are 

 other fresh-water species which have free jellyfishes. In this 



country we have a species/ 

 hitherto known only al:>out 

 Philadelphia, whose hydroid 

 stage is extremely small and 

 Ijears no tentacles. The jelly- 

 fishes are set free during July. 

 Freshwater jellyfishes have also 

 been described from Lake Tan- 

 ganyika, Africa, antl from a 

 tank at Regent's Park, London, 

 to which they had doulntless 

 lieen imported on plants. It is 

 very probable that all fresh- 

 water hydroids which produce 



Fig. 2.5.5. — Stylaftis, a tubularian 

 hj'droid, growing on a snail. Nat. 

 size. Photo, of living animal bv 



\y. H. c.p. 



Fil;. 2.50. — H,\"(lractinia, a tubularian hydroid. n, oolony growing on gastro- 

 pod shell inhabited \>y a hermit-crab : /', bit of eolon,\' enlarged ; dz. modi- 

 fied, tactile individuals; .s, reproductive individuals: sp, spines. From 

 Parker and Haswell. 



^ Microlnjdra Bijdcri. 



