620 



MARGARET ROBINSON. 



what is really needed is an examination of larvte intermediate 

 in age between the oldest which I have had and the adult. 

 But such evidence as we have at present seems to show that 



Text-fig. 5. 



Cn. 



oc 



31D 



■^--St 



Guathochilarium from adult Spirostreptus, with liypostome as usually 



present. 



only one pair of appendages (the second pair of maxillae) are 

 concerned in the making of the guathochilarium, though 

 the sternum of the segment which bears them most probably 



Text-fig. G. 



Go. - 



.QIII::^ ci^-Q---'"^ 



Cr 



::D 



-St. 



Gnatliocliilariuni from adult Spirost reptus, showing double liypostome. 

 Gn. Gnathochilarium. lly, liypostome. aS"^. Sleruum of post- 

 maxillary segment. 



also takes part in it. The fact that the suboosophageal 

 ganglion consists of only two pairs of ganglia seems to point 

 strongly to this conclusion, 



