132 



THE PHYSIOLOGY OF EARTHWORMS 



cells discharge into the capillary network surrounding the ganglion, 

 presumably mobiHzing the materials necessary to regenerate the 

 sexual apparatus (Hubl, 1953). 



More extensive experiments on this subject were carried out by 

 Herlant-Meewis (1957) with regard to the effect of the nervous 

 system on reproduction, egg laying and cocoon production. She 

 surgically removed (a) the cerebral ganglia, (b) the sub-oesophageal 

 ganglia, (c) the circum-oesophageal collar and (d) the ventral 

 nerve cord between segments 4 and 6/7. In case (a) the worms lose 

 weight, and the secondary sex characters such as the tubercula 

 pubertatis disappear and egg laying ceases. Egg laying begins 



Generol effects 

 on cyclic ociivities 

 such OS oestivotion 



Fig. 40. Possible pathways of neurosecretory interactions in an 

 earthworm. Letters indicate distribution of cell types. 



again after a delay of 8 weeks during which time the cerebral 

 ganglia regenerate. When the sub-oesophageal ganglia are removed 

 weight is lost only in the second week after the operation and is 

 regained in the fourth week. Cocoon productive capacity is lost for 

 2 to 15 weeks. Extirpation of the entire oral complex of the nervous 

 system interrupts egg laying for 7 to 17 weeks, and removal of the 

 ventral nerve cord immediately behind the oral region stops 

 production of eggs for 3 to 8 weeks. This last period is of the same 

 order as the delay in egg laying shown by controls in which 

 the body wall was opened but none of the nervous system was 

 removed. 



