PRODUCTION OF TWINS AND DOUBLE-MONSTERS 



339 



(Figs. 38 to 46 are from normally fertilized but crowded cultures) 

 Fig. 38 A very advanced twin larva in which much differentiation has taken 



place (see text). 



Fig. 39 A somewhat less advanced triplet larva. 



Figs. 40, 41, and 42 Examples of advanced twin larvae of various types 



showing differentiation of oesophagus, stomach, and intestine. 



