594 Fernon L. Kellogg. 



appears of full size and normal character in the adult insect, this is 

 not due to restorative regeneration, but simply to its normal growth 

 and development. If a leg be cut off in late larval life, the develop- 

 ing imaginal leg may or may not be at the same time mutilated. 

 If mutilated, however, it will always be by a removal of much less 

 of its extent than of the extent of the larval leg taken off. A 

 cut which severs the larval leg near its base (for example, through 

 the base of the femur,) will not take off more than the tarsus or 

 perhaps part of the tibia and tarsus of the imaginal leg, which, 

 in its development, is beginning to extend into the larval one. 

 Thus if the imaginal leg be found, when the imago issues, to lack 

 a tarsus but to possess a complete femur and tibia, this is no 

 indication that there has been a partial regeneration; there may 

 have been none whatever. 



To make a definitive test of the capacity of an insect with 

 complete metamorphosis to regenerate lost parts I have cut off 

 legs, both thoracic and abdominal (prop-legs) of the larvae of 

 the silkworm moth, Bombyx mori, at various ages, and have 

 noticed whether or not regeneration of these legs took place 

 before pupation, and if so in what degree and whether normally, 

 i. e., so as to produce an exact replica of the lost leg, or not. The 

 life of the silkworm larva is about 50 days (in the races which I 

 have used for study, and under the conditions attending their 

 rearing in my laboratory), and is divided by four moultings 

 into five approximately equal, active, feeding periods. In the 

 first and second period the larvae are too small to operate upon 

 satisfactorily, but after the second moulting the legs can be taken 

 off at any particular level desired. In the experiments silkworms 

 of several races, viz: Japanese white, Chinese white, Italian 

 yellow, Chinese crossed, etc., were used but the regenerative 

 phenomena in all were alike. 



Regeneration of Legs. 



The results of the experiments may be stated and illustrated 

 (see Figs, i to 10), as follows: In the first lots of individuals, 

 mostly of six each, one thoracic leg or one abdominal (prop-) 

 leg or one of each group of legs was cut off of larvae about 15 



