▁the ▁same ▁species ▁show ▁how ▁variable ▁aux in ▁responses ▁can ▁be . ▁ ▁Car rot ▁D au cus ▁car ota ▁was ▁the ▁first ▁and ▁most ▁understood ▁species ▁with ▁regard ▁to ▁development al ▁path ways ▁and ▁mole cular ▁mechan isms . ▁Time - lapse ▁tracking ▁by ▁To onen ▁et ▁al . ▁( 1 9 9 4 ) ▁showed ▁that ▁morph ology ▁of ▁compet ent ▁cells ▁can ▁vary ▁based ▁on ▁shape ▁and ▁cy top las m ▁density . ▁Five ▁types ▁of ▁cells ▁were ▁identified ▁from ▁emb ry onic ▁susp ension : ▁spher ical ▁cy top las m - rich , ▁spher ical ▁vac u ol ated , ▁o val ▁vac u ol ated , ▁el ong ated ▁vac u ol ated , ▁and ▁irregular ▁sh aped ▁cells . ▁Each ▁type ▁of ▁cell ▁multip lied ▁with ▁certain ▁geometric ▁symmetry . ▁They ▁developed ▁into ▁symmet rical , ▁asym met rical , ▁and ▁aber r antly - sh aped ▁cell ▁clusters ▁that ▁eventually ▁formed ▁emb ry os ▁at ▁different ▁frequencies . ▁This ▁indicates ▁that ▁organized ▁growth ▁polar ity ▁do ▁not ▁always ▁exist ▁in ▁som atic ▁emb ry ogen esis . ▁ ▁G ymn os per ms ▁Emb ry o ▁development ▁in ▁g ymn os per ms ▁occurs ▁in ▁three ▁phases . ▁Pro emb ry ogen y ▁includes ▁all ▁stages ▁prior ▁to ▁susp ensor ▁el ong ation . ▁Early ▁emb ry ogen y ▁includes ▁all ▁stages ▁after ▁susp ensor ▁el ong ation ▁but ▁before ▁root ▁mer ist em ▁development . ▁Late ▁emb ry ogen y ▁includes ▁development ▁of ▁root