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 Itthocysts, or 

 sacculi, containing one or more, rounded, concentrically 

 laminated masses of calcium carbonate (or phosphate,. 

 Hacckel), 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 nerves may pass from these ; but in general 

 this system is obscure, scarcely detectible. 



The relation between the gonophore and the 

 hydranth has been proved teratologically. Agassiz- 

 saw the sporosac of Rhizogeton, having discharged its 



