343 



According,- to Ruedemann's* observations 1 be young Diplo- 

 graptus upon leaving- the gonophore has already advanced! 



into the sicula stage, so that a free-swimming- planula stage 

 appears not to exist. It is probablethat this is 1 ruebf most, ; 

 if not all, graptolites, and that hence the distribution of 

 these animals is such as will be accounted for by the vicissi- 

 tudes which thev met with while a floating: colon v. 



Anthozoa. — The Anthozoa are typically marine sedentary 1 

 benthonic animals, inhabiting chiefly the warmer waters of 

 the oceans. A large number are without hard supporting 

 parts, and, consequently, leave no remains; while others* 

 probably the majority of Anthozoa, secrete a calcareous or 

 horny corallum, which is capable of preservation. Among 

 the Actinaria, or fleshy polyps, a certain amount of locomo- 

 tion of a creeping or gliding nature is often observable 

 (Metridium, etc.), the individuals possessing this ability 

 thus passing from a normal sedentary to a vagrant ben- 

 thonic life. A few forms are also met with among the plank 1 

 ton. Occasionally, pseudo-planktonic individuals are Met 

 with attached to floating algte or timbers, and pseudo- 

 vagrant benthonic individuals attached to moving crusta- 

 ceans are not unknown. 



The Madreporaria, or stone corals, are normally seden- 

 tary forms, though they are not necessarily attached, but 

 may rest upon the sands. (Fungia, some Porites.) Though 

 the normal medium of the Anthozoa is salt water, a few are 

 known in brackish and even in tolerably fresh water. • Cilicid 

 rubeola, is reported by the "Challenger"! in the river Thames 1 

 in New Zealand ; and Dana$ states that " * * * upon the 

 reefs enclosing the harbor of Rewa (Viti Lebu), where a 

 large river, three hundred yards wide, empties, which during' 

 freshets enables vessels at anchor two and a half miles off 

 its mouth to dip up fresh water alongside, there is a single 

 porous species of Madrepora (M. erihripora), growing here 



■ ' ! . . , ! 



*Ruedemann, R., Development and Mode of Growth of Diplograptus. McCoy. 14th 

 Ann. Rep. N. Y. State Geol., 1895, pp. 219-249, Pis. I.-V. 



+ Report, Vol. XVI., H., p. 36. ^ . 



X Corals and Coral Islands, 1872, p. 120. 



