海(hai)(hai)參的(de)(de)內骨(gu)(gu)骼多(duo)(duo)不發達,變為須用顯微(wei)鏡(jing)才能(neng)看(kan)見的(de)(de)許多(duo)(duo)微(wei)小石灰質骨(gu)(gu)片(pian)(pian)埋沒(mei)于(yu)外(wai)皮(pi)之(zhi)下(xia),數目一般都很(hen)(hen)多(duo)(duo)。觀察骨(gu)(gu)片(pian)(pian)應作(zuo)些處理,最(zui)簡單(dan)的(de)(de)方法是取一小片(pian)(pian)皮(pi)膚,置于(yu)玻片(pian)(pian)上,然后滴1-2滴次(ci)(ci)氯酸鈉溶(rong)液于(yu)皮(pi)膚上,1-2min,次(ci)(ci)氯酸鈉溶(rong)液會把皮(pi)膚組織腐蝕掉,而剩下(xia)骨(gu)(gu)片(pian)(pian),再(zai)加1-2滴蒸餾水,蓋上蓋玻片(pian)(pian),置于(yu)顯微(wei)鏡(jing)之(zhi)下(xia)便(bian)能(neng)觀察清楚。海(hai)(hai)參骨(gu)(gu)片(pian)(pian)形狀美麗而多(duo)(duo)變,是海(hai)(hai)參分(fen)類最(zui)重(zhong)要(yao)的(de)(de)依據,常(chang)見的(de)(de)骨(gu)(gu)片(pian)(pian)有桌形體(ti)、扣狀體(ti)、桿(gan)狀體(ti)、穿孔(kong)板、花紋樣體(ti)、輪(lun)形體(ti)和錨形體(ti)等(deng)。海(hai)(hai)參骨(gu)(gu)片(pian)(pian)數量(liang)很(hen)(hen)多(duo)(duo),有人計算(suan)過1個(ge)丑海(hai)(hai)參有約2000萬個(ge)骨(gu)(gu)片(pian)(pian)。
海(hai)參咽部(bu)圍繞一環鈣(gai)質骨板,稱(cheng)(cheng)為石(shi)灰環,由10塊骨板組成(cheng),5個輻(fu)(fu)位的骨板,稱(cheng)(cheng)輻(fu)(fu)片,5個間輻(fu)(fu)位的骨板,稱(cheng)(cheng)間輻(fu)(fu)片。石(shi)灰環是海(hai)參特有的器官(guan),它可能和海(hai)膽的亞里斯(si)多德提燈同源。石(shi)灰環形態(tai)在海(hai)參分類上也很重要。