MICHIGAN ACADEMY OF SCIENCE. 



103 



Fig. 4. 



EXPLANATION OF FIGURES. 



Dactylozooid . x tm 



Female blastostyle x 9b 



Gasterozooid x 38 



Male blastostyle ,x i)o 



Tentaculozooid x l.SO 



A colony of Hydractinia polyciina grow- 

 ing on an Euijagiirus shell. 



Cross section of male gonophore x 413 



Cross section of female gonophore x 413 



Cross section of gasterozooid, middle 



region x 413 



Cross section of skeleton x 152 



Ch Chitinous skeleton 



E Egg. 



cc Ectoderm. 



En Endoderm. 



O Gonophore. 



O.C Gastral cavity. 



h Hypostome. 



Z/. Ec. .. .Lower Ectoderm. 

 L. En. . . . Lower endoderm. 

 M Mouth. 



REFERENCES ON PLATES. 



mcs Mesogloea. 



n Nucleus. 



n.c Nucleolus. 



R.T Rudimentary tentacles. 



S.c Sperm cells. 



<S'p Spine. 



T Tentacle. 



up. ec. . .Upper ectoderm. 

 Mp. en. . .Upper endoderm. 



