124 



THE ANATOMY OF INVERTEBRATED ANIMALS. 



ments (Fig. 28, III.). The ova or the spermatozoa pass out 

 of the apertures of the genital chambers,, and tiie ova are re- 



Fig. l^.—Cephea ocellata (?).— The entire animal : a, the umbrella ; b, the ramifications 

 of the brachia ; c, the tentacles which ferminatc them; o. the pillars wiiich sus- 

 pend the biacliit'erous disk which forms the floor of the siib-umbrollar cavity ; /, 

 short clavate tentacles between the oral pores. 



ceived into small pouches or folds of the lips, and there under- 

 go the preliminary stages of their development. 



In the Mhizosto'inidce (as was originally suggested by Yon 

 Baer and has been proved by L. Agassiz and A. Brandt ^ ) 

 the margins of the lips of the hydranth unite, leaving only a 

 multitude of small apertures for the ingestion of food on the 

 long arms, which represent prolongations of the lips of the 

 hydranth (Figs. 19, 20, 21). The polystomatous condition 

 thus brought about, by the subdivision of a primitively sim- 

 ple oral cavity, is obviously quite different in its nature from 

 that which occurs in the Porifera. 



In most of the HJdzosto^nldce^ not onl}^ do the edges of 

 the lips unite, but the opposite walls of the hydranth beneath 

 the umbrella are, as it were, pushed in, so as to form four 



» "Memoires de I'Academie de St.-Petersbourg," xvi., 1870. 



