1901.] NATURAL SCIENCES OF rill LADELFIKA. 679 



close proximity of the braia lobes. The dorsal and ventral lobes of 

 each side are connected anteriorly, as may be seen from sections, but 

 the conuectiou ends just posterior to the end of the ventral com- 

 missure, and from this point backward the dorsal and ventral lobes 

 are quite separate. In life the ganglion cell layer appears distinct 

 from the fibrous core of the brain and lateral chords, the former 

 as a greenish-yellow investing layer, the latter as a clear silvery- 

 gray central mass. 



From sections it may be seen that both dorsal and ventral lobes 

 are continued forward into the tip of the head as numerous slen- 

 der nerves, which are approximately represented in Plate XL, fig. 

 1. No especial nerve endings have been observed. The dorsal 

 lobes terminate as such just in front of the cerebral organs, and from 

 their posterior ends arise the nerves that supply the cerebral 

 organs. Immediately in front of the cerebral organ, the dorsal 

 lobe gives off on its dorsal side a horn or prolongation of the 

 fibrous core surrounded by ganglion cells. This horn ends shortly 

 and is replaced posteriorly by the cerebral organ, but there is no 

 connection between the two structures, for the cerebral organ derives 

 its nervous matter from the ventral part of the dorsal lobe. The 

 cerebral organ nerve enters the cerebral organ on the ventral side 

 and afterward branches and ramifies, so that the nervous material 

 is well distributed throughout this sensory organ. 



The ventral lobes are continued backward throughout the body 

 and caudicle as the lateral nerve chords (" Seitenstiimme "), fig. 1, 

 L.N., but do not unite posteriorly in an anal commissure. 



The paired cesophageaJ nerves, fig. 16, Oc.N., arise from the ven- 

 tral lobes in the same frontal plane as the cerebral organs, but con- 

 siderably ventral to them. A slender commissure, fig. 16, Oe.N. 

 Comm., is formed between them, .08 mm. behind their origin, out- 

 side the circular muscle layer, just anterior to the mouth, 31. 

 ]5ehind the commissure the nerves pass through the circular and 

 inner longitudinal muscle into the tissue around the mouth, occa- 

 sionally giving off branches, and continue backward into the 

 oesophageal region. Here they break up into numerous fine 

 branches which ramify in the walls of the oesophagus, not only on 

 the ventral side but also laterally, and which are very abundant 

 on the dorsal side. 



From the dorsal commissure arises the median unpaired upper 



