150 Journal of Comparative Neurology. 



size are also found that enter into the fibrillar substance more 

 deeply, and gain their entrance along with some nerve fiber or 

 bunch of fibers. 



In no case have I been able to make out a tracheal net- 

 work such as described by Emil Holmgren (95) for the spin- 

 ning glands of lepidopterous larvae. So far as bichromate of 

 silver preparations thus far made show, the branchlets all termin- 

 ate independently of one another. In some of my copper-haema- 

 toxylin preparations there are, however, certain details that re- 

 tall Holmgren's figures which lead me to suppose that a 

 tracheal network may exist. 



Special Description— the Proto-cerebron. 



THE MUSHROOM BODIES. 



From this hasty general account of the brain and its con- 

 stituent elements I pass to a more detailed consideration of its 

 parts and choose for the first the mushroom bodies as being the 

 most conspicuous and as the better serving for the orientation 

 of other parts later to be described. 



These organs were first noted by Dujardin ( 50) in a study 

 of transparent preparations in toto. From their slightly lobular 

 or folded appearance he compared them with the convolutions 

 of the human brain and described them as "lobes a convolu- 

 tions " probably associated with the intelligence of the insect. 

 As will be seen in the sequel, this supposition has very much 

 more in its support than the crude or undeveloped morphologic 

 cal technique of that time was capable of bringing to light. 

 Later they were again found by Leydig ( 64) who mentions 

 them under the term " Gestieltes Korper. " They were again 

 described by Rabl-Ruckhard ( 75) who, according to Viallanes 

 ( 87)> first correctly described the calyx. But it was not until 

 Dietl ( 76) had applied microtomy and stained his sections with 

 osmic acid that a complete description of their whole structure was 

 obtained. Since that time they have been so often re-described 

 for insects representing the different orders of hexapods that 

 they may be considered as fairly well known structures very 



