Introduction to Animal Morphology. 89 



long, tubular, or septate and contractile. In their 

 bulbous bases, imbedded in the ectoderm of the gono- 

 chemes, are masses of black or red, homogeneous, 

 pigment spherules (ocelli), often with a clear, reflecting 

 body immersed, and sometimes with a nerve ganglion 

 at their bases. Around the margin of the bell in 

 blastochemes, in the mid-spaces between the tentacles, 

 or sometimes irregularly distributed, are lithocysts^ or 

 sacculi, containing one or more, rounded, concentrically 

 laminated masses of calcium carbonate (or phosphate, 

 Ifacckcl\ rarely crystals, as in Cunina. These bodies 

 are longitudinally striated, and sometimes (Geryonidae) 

 a ganglion lies under each sac, and fine hairs go to 

 the concretion. In Tiaropsis, a pigment spot exists 

 at the base of the lithocyst, but otherwise ocelli and 

 lithocysts do not co-exist. Some lithocysts are 

 pedunculated, and a canal from the marginal vessel 

 passes into each, ending in an ampulla, below which 

 is the vesicle containing the otolith. Ocelli rarely 

 occur in blastochemes (except in Thaumantias, &c.) ; 

 nor lithocysts in gonochemes (except in Goodsirea) ; 

 Melicertum 'a blastocheme) has neither. 



Fine bristles (touch-organs) are found in the epi- 

 thelium over the ganglionic swellings at the bases of 

 the lithocysts in Cunina, and over the tentacles in 

 Rhopalonema. The nerve system may consist of a 

 ring connecting these ganglia, and true nerve cells 

 have been found in the latter. Radial and inter- 

 radial :nay pass from th-se; but in general 

 this system is o1 -carcely d'-t<-rtible. 



'Ill" n-lation between the gonophore and the 



hydranth has been proved t<-ralnl<Lrirally. Agassiz 



tc of Rhizogeton, having dis< -harvard its 



