EFFECTS OF DUCTLESS GLANDS ON FLIES 257 



The method of procedure in the experiments made was very 

 simple. The food material with the eggs on it was placed in 

 ordinary glass tumblers having a capacity of about 200 cc. which 

 were covered with voile fastened with a rubber band. By 

 examining the glasses several times a day any eggs deposited on 

 the voile may be removed before they hatch and contaminate the 

 culture. In later experiments a canopy of mosquito netting was 

 stretched over the glasses to prevent the near approach of flies. 

 When it was desired to obtain the pupae, it is more convenient 

 to place the food in a Petri dish and place this upon a layer of sand 

 1 or 2 cm. deep in the bottom of a large culture glass 200 cm. in 

 diameter. This large dish was covered with a glass plate elevated 

 at one side by a few folds of paper for ventilation, and the whole 

 was covered with a mosquito net and kept shielded from direct 

 sun light. The culture dishes were always kept side by side under 

 as nearly identical conditions of illumination and temperature as 

 possible and in order to reduce any accidental differences, the 

 positions of the dishes were reversed from time to time. As far 

 as possible, in each observation a single egg mass was employed, 

 one portion was used for the experimental feeding and the 

 other for the control. 



It is somewhat difficult to handle the eggs of the flesh flies with- 

 out injury because of their stickiness. In consequence it fre- 

 quently occurred that the division of the egg mass was far from 

 equal. 



The glands used for food were obtained fresh from the slaughter 

 house and for the most part were obtained from calves, although 

 some were obtained from steers and sheep. The control food was 

 a mass of muscle approximately equal in bulk to the thyroid or 

 thymus used . An ad van t age in using these relatively small m asses 

 of food is that the heating due to active putrefaction is less. 



The effect of the ductless glands on growth and differentiation 

 was measured by the length of the larvae, the length of the 

 pupae, and the duration of the larval and pupal stages. 



In order to measure the larvae, they were killed by immersion 

 in boiling water or 95 per cent alcohol. Both these agents 

 seemed to cause very little contraction or distortion. It was 



