APPENDIX. 



(Abstracts or summaries of papers already published by the author on various 

 phases of silkworm biology.) 



(with R. G. Bell) Notes on Insect Bionomics, in Jour. Exper. Zoo!., 

 V. 1, pp 357-367, August, 1904. 



Food Conditions in Relation to Sex Differentiation. — ^Various lots of silk- 

 worms were reared on reduced rations in the years 1901, 1902, and 1903, to 

 test the alleged influence of nutrition on sex differentiation. It has been 

 assumed by some authors that poor nutrition of developing organisms is an 

 extrinsic influence tending to determine the sex of the organism to be male 

 and good nutrition an influence tending to produce females. The most impor- 

 tant part of the assumption is the idea that sex is subject to control by the 

 environment of the organism — that sex is not inherently predetermined in the 

 germ. 



The data obtained test the possible influence of poor nutrition of the parents 

 (and grandparents) in determining the sex character (if predetermined) of 

 the germ cells, as well as of the possible immediate influence of nutrition in 

 determining the sex of developing individuals. 



No positive influence of the poor nutrition on sex determination of the 

 silkworm is shown by the data presented. 



Forced Pupation. — Experiments were made to determine how early in 

 larval life the food supply could be cut off without stopping the metamorphosis 

 (development) of the silkworm, whether such forced abbreviation of the food- 

 taking period results in any unusual structural or physiological modification 

 in the stages which follow the withdrawal of food, and whether the metamor- 

 phosis (in particular, pupation) is hastened when food is withdrawn in late 

 larval life, an adaptation often assumed to be possessed by Lepidoptera. Such 

 an adaptation would obviously be of real advantage, as it might often save 

 individuals from death due to a sudden disappearance of the food supply, or 

 to sudden accidental incapacity to gain access to the food supply. 



The silkworm race experimented with in this regard spends normally about 

 sixty days in the larval (feeding) stage, divided into five actively feeding 

 intermoulting periods of about ten days each, by four brief two-day moulting 

 periods, during which no food is taken. On the eleventh or twelfth day (from 

 270 to 300 hours) after the fourth moult, the larva "spins up" and pupates. 



Twenty healthy silkworms were selected at random from a large lot 

 (several hundred) which had been reared in one tray, all the individuals, of 

 course, under the same condition of food supply, temperature, humidity, light, 

 etc. Of the twenty, one was fed as long as it would take food; the other 

 nineteen were deprived of food variously from the time of the fourth moult, 

 from one day after the fourth moult, from two days after, from three days 

 after, and so on until individuals were obtained representing a withdrawal of 

 food supply for a period of but a day before the normal time of giving up 



