136 Mr. P. A. Buxton on the 



From a consideration of what is known about similar organs 

 in other insects I do not consider that much doubt exists 

 as to the functional connection between these small, round, 

 deeply placed lobes and the ocellus. It is hardly to be ex- 

 pected that we should be able to find more than a propor- 

 tion of the smaller tracts in so minute a structure as the 

 brain with which we are dealing. Fibres pass from the 

 ocellary glomerulus to many parts of the brain, including 

 the paired (deuterocerebral) sympathetic system (tract s) 

 and the posterior part of the antennary lobe (tract t). 



B. The Optic Lobes. 



Pressure of other work has absolutely prevented my 

 devoting attention to the optic lobes (o. I.), and much special 

 study of the literature would be required before I could 

 hope to treat of them at all adequately; this would 

 delay the publication of this paper almost indefinitely, 

 and I have accordingly decided to leave them entirely 

 undescribed rather than to deal with them in an inadequate 

 manner. 



VII. The Protocerebral Tracts. 



Authors have frequently attempted to enumerate the 

 tracts of fibres which connect one part of the brain with 

 other parts, but they can only detect and describe the larger 

 bundles and can never even attempt to follow the minute 

 tracts which ramify in all directions through the Punkt- 

 substanz. Such an enumeration must always be incom- 

 plete even if one part of the brain is proved to have a score 

 of paths connecting it with other regions : and even if the 

 Golgi method is applied to a very large number of individ- 

 uals, definitive completeness can hardly be arrived at. In 

 this present paper I make no attem])t to give any complete 

 list : I only describe a few of the more noticeable tracts 

 which are useful either as landmarks or else as definite 

 boundaries to regions. 



The following tracts should perhaps be noticed, because 

 they are important features of the sections in which they 

 occur, (a) A ^^^de tract of fibres arising from cells situated 

 over the dorsal part of the protocerebrum, and passing 

 vertically downwards in the middle line over the front of 

 the protocerebral lobes : this tract forks below and the 

 fibres then pass to the antennary lobe of each side, and 



