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a hydranth bud is -et with v.'hich has six tnntncular rrr- 

 .-iecticps ard thus rives rise to six rri'-'ary trntrrles. 

 The -^outh is '^ov,' devplcred, as r. slit breaking thrcurh the 

 two ger-^ layers, at the a-pex of the yourr hydra-th i-^ the 

 centre of the '.vhorl of tertacular buds. About a day later 

 T-ore tentacles a^^r^ear. These secondary tentacles alter- 

 nate v/ith the '-'ri-ary ones. The secondary tentccular buds 

 do not all arsnear si-^ultaneously; but are usually added one 

 or tv.'C at a tire u"'til the second cycle of tentacles is rorr-- 

 rleted and the hydra-th has ten te-tacles in all. :hus 

 we ray have ycu-^F hycranths vnth six, seven, elrht, n:ne or 

 te- tentacles acccrdinp to the stape cf revelcrrent. 

 Ten seerrs to be the nuTber cf tentacles in the fully 

 develc^ed hydi;!/^ rclyn. The oldest nolyps thst I reared 

 five days old ha;' this number; and Professor Brcol's described 

 the hydr,3/0d, yhich he found or the Icrer surface of the 

 shell of the livinr li'ulus, arid which had -edusr buds, 

 develcned, as hcving only ten tentrcles. The hydra-^ths 



