410 N. E. MCINDOO. 



chloroform where they remain five minutes. They are then em- 

 bedded in 55° M.P. paraffin for five minutes. The sections were 

 cut from five to ten microns in thickness and when they failed 

 to ribbon the microtome knife was warmed. From this stage 

 on the sections are treated like ordinary parafifin sections with 

 the following exceptions. A rather thick film of fresh Mayer's 

 albumen is spread upon each slide. After drawing the water 

 from the slide upon which are mounted the sections, the latter 

 are flattened to the slide by using a piece of wet tissue paper. 

 No heat is used for straightening the ribbons on the slides because 

 the least amount of heat blisters the celloidin. After drying 

 over night, most of the sections adhere to the slides while being 

 passed through the reagents, but to be sure of not losing any 

 sections, the slides were sometimes wrapped in tissue paper and 

 thread was then firmly wound around the paper. Instead of 

 using absolute alcohol a mixture of equal parts of absolute 

 alcohol and chloroform is employed so that the celloidin may 

 not be dissolved, and instead of using eosin in 95 per cent, alcohol 

 as a counter stain, the eosin is put into a mixture of the absolute 

 alcohol and chloroform. The sections were stained in Ehrlich's 

 hematoxyHn from 10 to 15 minutes, the time depending on 

 their thickness and whether or not they were wrapped in tissue 

 paper. 



The writer is grateful to Mr. H. S. Barber of the Bureau of 

 Entomology for most of the dried specimens used which belonged 

 to the collections of the U. S. National Museum. Mr. Barber 

 is also to be thanked for the identification of all the beetles used 

 in the experimental part of this work. 



MORPHOLOGY OF THE OLFACTORY PORES. 



Before experimenting to determine the function of the organs 

 called the olfactory pores by the writer ('14a), the distribution 

 and number of these pores in many beetles were studied. 



Disposition. 



In making a comparative study of the disposition of the ol- 

 factory pores in beetles, 50 species, belonging to 47 genera and 

 representing 34 families, were used. With the exception of two 



