16 B. H. BUXTON 



these I was able to keep alive for two months, fixing four or five 

 for sectioning every few days. In the larval stage the spiders 

 were very inert, with distended abdomen containing a large 

 amount of yolk. They were not pigmented and remained 

 quiescent in the cocoon. At the end of a month they all 

 moulted simultaneously and left the cocoon, passing from the 

 larval to the immature stage. They were now pigmented, long- 

 legged, with small abdomen, and very active, remaining so until 

 the last of them had been killed for sectioning a month later. 

 These points are merely mentioned to show that the spiders were 

 in a normal condition, at any rate in the early stages. 



In the youngest specimens five abdominal ganglia were clearly 

 distinguishable, but the ganglia rapidly disappeared and in 

 about a week there were no traces left. I do not think that any 

 observation of these transient abdominal ganglia in spiders has 

 ever been recorded. 



In specimens killed at once and two days later, the suboeso- 

 phageal ganghon contains twelve neuromeres very clearly mapped 

 out. From its posterior end two parallel nerve cords pass 

 through the pedicle, beyond which they separate, running later- 

 ally and ventrally in the abdomen. On either side of the abdo- 

 men are three very clearly defined, large ganglia, connected to- 

 gether by the nerve cord. The nerve cord can be traced a little 

 beyond the third ganglion, where it is lost, but more posteriorly 

 there are two very much smaller ganglia ying in the neighbor- 

 hood of the intestinal tract, which has so far only partially been 

 formed. The rest of the abdomen is filled with yolk (diagram 5) . 



In specimens fixed three days later (five days after finding the 

 cocoon) the nerve cord was no longer traceable into the abdo-. 

 men; the two posterior ganglia had disappeared and the three 

 anterior were greatly diminished in size. 



On the seventh day there were some traces of one or two 

 ganglia, but it was difficult certainly to identify them, and this 

 was the last trace of them that could be found. If the series 

 had begun at this stage the gangha would certainly have been 

 overlooked or not recognized as such. 



