SIPHONOPHORA 



167 



^>can.r. 



cor. 



—med. 



Fig. 124. Development of the siphonophore colony. A, Diagram of the 

 possible combinations of individuals in a colony. The continuous gastro- 

 vascular system is shown in black, pn. pneumatophore ; nee. nectocalyx; 

 hyd. hydrophyllium ; gst. gastrozooid; dac. dactylozooid with its tentacle; 

 gnz. gonozooid ; cor. cormidium ; esc. coenosarc ; ten. branched tentacle, 

 sometimes springing from the base of the gastrozooid. B, Early stage of colony 

 of Muggiaea, showing two generations -of nectocalyces, nec.^, nec.^ can.r. the 

 radial canals of the first nectocalyx. Other lettering as in A. nec.^ is lost later 

 and nec.^ becomes the single permanent nectocalyx of the colony ;/)w. is really 

 an oleocyst and not a pneumatophore. C, Sarsia, an anthomedusan, for 

 comparison, showing budding of daughter medusae from the end of the 

 radial canals, mnb. manubrium; med. daughter medusae. A, altered from 

 Hertwig; B, after Chun; C, after Allman. 



