126 THE NERVOUS SYSTEM [CH. 



large clear nuclei, each carrying a large darkly-staining nucleolus. 

 Many of them are of very great size. They have been compared 

 with the cells of Purkinje in the cerebellar cortex of Mammals. 



Various authors have stated (i) that the mushroom bodies of 

 the Dragonfly's brain are rudimentary, (ii) that this indicates, or 

 corresponds with, the possession of a very low order of intelligence. 

 Neither of these statements is justified by the facts. The mushroom 

 bodies of the Dragonfly's brain are certainly not rudimentary. On 

 the contrary, they are very well developed, though of a generalized 

 type which makes them appear poorly developed when compared 

 with the highly-specialized structures to be seen, for instance, in 

 the brain of the wasp. Nor is the intelligence of the Dragonfly 

 by any means of a low order, in comparison with that of most 

 insects. "Intelligence" may be developed through the use of the 

 sense of sight as well as through other senses, but such intelligence 

 is not to be placed on a lower order than that developed, for 

 instance, through the senses located in the antennae. Judged 

 broadly on its activities and powers of perception, the Dragonfly 

 must certainly be classed as a more "intelligent" insect than 

 many of those which possess more complicated mushroom bodies, 

 if indeed the word "intelligent" can be properly applied to these 

 creatures. The implied assumption that the mushroom bodies 

 are the sole seat of "intelligence" seems to be quite unwarranted. 



The protocerebrum gives off the following nerves : 



(i) The optic nerves, described in connection with the optic 

 ganglion (p. 130). The optic tubercle (ot) is the internal termination, 

 in the procerebral medulla, of the superior portion of the optic 

 nerve. 



(ii) The nerves to the lateral ocelli (ocln). These are rather 

 elongated, and about as thick as the antennary nerves. They 

 arise from two small cell-masses placed in the upper posterior 

 portion of the procerebral cortex. 



The paired nerves to the median ocellus are said by the latest 

 observers to arise from the deutocerebrum. They are best dealt 

 with here, however, since, in the Dragonfly at any rate, their 

 whole course is to be followed within the protocerebrum. Arising 

 far apart and posterior to the level of the central body, they run 

 obliquely upwards and inwards to meet in the middle line, well 



