310 



ESSENTIALS OF ZOOLOGY 



expanded and contracted, and it can change its location by ''scooch- 

 ing" on its basal disc (attached end). The mouth is located in the 

 center of the crown. 



Asexual reproduction by budding from the margin of the basal 

 disc is practiced by this animal. Occasional lougitudinal fission may 

 occur. The gonads develop on the edges of the lower part of the 

 septa to provide for sexual reproduction. The sexes are distinct. 

 Mature ova and spermia are discharged into the water of the cavity 

 and escape through the mouth to unite in fertilization outside. 



P«riit< 



MoutK 



p T«nttcle« 



Tertiary Mesentery 



Conad 



Primary Meaeniery 

 B 



Meienterial filament 

 5econdary Meientery 



Cincladc. vrith 

 Acontium protrudiftf- 



Stereogram of Anthozoan Polyp 



Meaenterie fiUmeni 



Doraal 



5)pKo no glyph 



£:amo(laeum 



Primary 

 Mcaenleriea 



Seedndary 

 .Mesenteriea 



Tertiary 

 **Mcacnterict 



...-. Hollow 

 Tent* da 



' Sphincter 



Diagrammatic T. S. of Anthozoan Polyp ^t level A*A 



Endoeoel. chamber between 

 two metenteriet of « 

 the tame pair ^ 



Csoeoel. chamber 

 between paira ^ 

 of meacntcrica *^ 



Di raciivca 

 (Ventral 5cr of 

 Primsry Mcaenlen^a) ** 



Meientefie 

 , filament 



Seeonilafy 

 , Mesentcrica 



^ Primary 



" Mocntcriea 



**«^ Terli«ry 

 Metcnteriea 



Diagrammatic T 5. of Anthozoan Polyp at fevel B-B 



Fig. 109. — Diagrams showing structure of the anthozoan. Metridium, (Courtesy of 



Pacific Biological Laboratories.) 



Order Madreporaria. — The representatives of this order secrete an 

 external limestone skeleton; most of tliem are colonial. Astraiigia, 

 Madreporay and Oculina are examples. 



Astrangia is the common coral polyp, and it is quite similar to a 

 small sea anemone to which calcium carbonate has been added by 

 secretion from the ectoderm cells as well as having budded to form 

 a colony of numerous individuals. In time continually growing colo- 



