496 



M (/REACH. 



in the ectoderm, and migrate toward the free end of the larva 

 — corresponding with the pointed end of the planula. Usually 

 two opposite tentacles bud out next, though many cases have 

 been observed where only one appeared, and others where two 

 tentacles appeared at right angles to each other. 



Thus we have arrived at a hydrula stage, and, so far as this 

 goes, we have true alternation of generations. 



Woods Holl, Mass., 



August 20, 1895. 



