EXPERIMENTS WITH CHRYSOMELID BEETLES. 



249 



The preparation shown in Fig. 17 is from an egg fixed one day 

 after the posterior end had been killed, and is the same age as 

 that of Fig. 15, i. e., three days old. It is of special interest, 

 since the end of the tail fold (//), which was not killed by the 

 operation, has continued to develop, although it is an extremely 

 small piece of tissue and was separated from the rest of the living 

 embryo by a considerable amount of yolk. The anterior part 

 of the embryo consisting of the cephalic region and the first 

 thoracic segment, developed normally. During the twenty-four 

 hours between the operation and fixation, the living part of the 



ab 



17 



FIG. 17. Side view of an egg of Lepiinotarsa decemlineala three days old (L.D. 

 016 Ci). The posterior end (k) was killed when the embryo had reached the stage 

 shown in Fig. 4; the anterior end continued to develop and has come to lie on the 

 right side of the egg. ab, abdomen; h, head; t, thoracic appendages; tf, tail fold; 

 y, yolk. 



FIG. 18. As in Fig. 17 four days old (L.D. 016 2). 



embryo contracted and left a large yolk space (3;) between it and 

 the killed material (k). A similar condition was noted above 

 in series L.D. 04 A3, Fig. 13 (y). 



Fig. 1 8 represents an embryo (L.D. 016 C2) which was allowed 

 to live one day longer than that just described. Here the head 

 and first thoracic segment have continued to develop reaching 

 a stage similar to that shown in Fig. 6. This part of the embryo 

 has changed its orientation since the operation and now lies 

 on the right side of the egg instead of on the ventral surface. 

 Several other cases like this were observed in series L.D. 016 

 and in a number of the embryos from other series of experiments. 



