28 SOURCES OF KINETIC AND METABOLIC HORMONES 



It has been suggested that, in addition to acting as a storage- 

 and-release organ for the neurosecretion, the walls of the sinus 

 gland may include some secretory cells, but of this there is no 

 clear evidence (Knowles and Carlisle, 1956). It seems more likely 

 that active hormones are being set free here from the inactive 

 carrier substance that travels down the axons. 



In the sessile-eyed Malacostraca, such as the Isopoda, both the 

 ganglionic-X-organ and the sinus gland itself lie within the head 

 capsule (Amar, 1948). 



Hanstrom^s sensory pore organ 



The sensory pore organ, like the sinus gland, is the storage-and- 

 release organ for neurosecretory cells some of which are situated 

 within the brain and others in the ganglionic-X-organ. All 

 the axons have their endings swollen into characteristic onion- 

 shaped bodies in Hanstrom's sensory pore organ, situated on 

 the ventral surface of the eyestalk in Malacostraca (Fig. 2-6). In 

 addition to these axon endings and to the sensory cells, which 

 give their name to the organ, there are some small secretory cells 

 confined within the organ, at least in Lysmata (Carlisle and 

 Passano, 1953). 



This structure was originally called the "X-organ" and was 

 identified in several species by Hanstrom (1939) and his pupils; 

 but since then, many workers have used the name X-organ for the 

 neurosecretory cell bodies located in the terminal medulla. The 

 modified name of ganglionic-X-organ is here used for this latter 

 group of cells, from which in fact axons run to both the sinus gland 

 and to Hanstrom's organ (Knowles and Carlisle, 1956). 



Commissures and connectives 



Active extracts have been obtained from many other parts of 

 the crustacean nervous system besides the supraoesophageal 

 "brain"; but as yet there is little indication of where any natural 

 hormones, corresponding in their actions to these extracts, may 

 be released into the blood stream. 



The tritocerebral (or antennal) commissure, which is a cross 

 connection passing below the oesophagus between the tritocerebral 

 parts of the brain (Fig. 2-5«), is particularly rich in chromactivat- 



