NEUROSECRETION 133 



Histological examination of the ganglia from animals at various 

 times during these processes indicates that two separate systems 

 are involved. The removal of the sub-oesophageal ganglion is 

 followed by an accumulation of secretory and colloidal material 

 within the a-ctlh of the cerebral ganglion. This leads to the 

 suggestion that the cells, known from the work of Hubl (1953) to 

 affect reproduction, do so not by a direct action upon the gonads, 

 but by an indirect method, first stimulating other neurosecretory 

 cells within the sub-oesophageal ganglion to discharge their 

 products. Hubl (1953) states that the «-cells discharge into the 

 capillary network surrounding the cerebral ganglion and as this is 

 interrupted when the sub-oesophageal nerve mass is removed 

 there is no continuity between the two neurosecretory systems. 

 The secretions are evidently not released into the coelom since this 

 is always in contact with both nerve concentrations and is not 

 interrupted by the removal of either, or by severance of the 

 circum-oesophageal commissure. Removal of the cerebral ganglion 

 is likewise followed by the appearance of concentrations of 

 secretory materials within the sub-oesophageal ganglion. This 

 material sometimes also makes an appearance in the axons leading 

 from this gland. Egg production in this case ceases immediately. 



To summarize then it is evident that the «-cells of the cerebral 

 ganglion play a regulatory part in the reproductive cycle of the 

 earthworm. They show a regular cyclic production of secretory 

 material within the cells and release their products into a capillary 

 blood supply in the spring-time when the gonads come to maturity, 

 their action being mediated through a second set of secreting cells 

 in the sub-oesophageal ganglia. Marapao (1959) has also adduced 

 evidence for a hormonal transmission of brain substances since 

 injection of brain extracts mimics the effects obtained from 

 intact animals. 



Although it is not to be supposed that changing day length has 

 any effect upon the neurosecretory activities of the ganglia of 

 earthworms it is interesting to note that sunlight, ultra-violet 

 illumination and darkness all affect secretory cells (Aros and Vigh, 

 1959) (see Toro, 1960). The medio-dorsal cells ( = ^-cells of Hubl?), 

 and the lateral secretory cells in the segmental ganglia show vacuoli- 

 zation and discharge when the animals are placed in visible or 

 ultra-violet light. Replacement in the dark leads to a further 



