No. 437.] COMPOUND EVES OF MACHILIS. 



321 



moulted every seven days though no one insect lived longer than 

 three weeks. 



Methods. — This study was made entirely from serial sections. 

 Some of the sections were cut five microns thick but owing to 

 the difficulty of obtaining such thin sections through the chitin, 

 the greater part of the material was cut ten microns thick. 



In preparing the eyes, the animals were first killed by being 

 dropped into hot water after which the heads were placed in 

 the fixing reagent. Before the heads were cut off, the antennas, 

 palpi and as much as possible of the pronotum were removed 

 since it was found that these parts, if left on the head, interferred 

 with the process of imbedding and cutting. The removal of 

 these parts had to be done with great care for the pressure of 

 the hand in holding the animal often caused a distortion of the 

 parts of the eye thus ruining the material for study. 



Of the many different fixing reagents tried the best results 

 were obtained with Flemming's fluid, Picro-sulphuric acid, and 

 platino-aceto formaldehyde. The eyes were cut in paraffin after 



