XEW ORGAN IN PEIJI ['LANETA OKIENTAUS. 



Prelimiuary Account of a New Organ in 

 Periplaneta orientalis. 



By 



Kutli M. Harrison, 



Lady Margaret Hall, Oxford. 



With Plate 15. 



While dissecting a cockroach in the Zoological Laboratory 

 at Oxford I noticed a pair of small oval pouches lying below 

 and to either side of the nerve-cord between the fifth 

 and sixth abdominal ganglia. Being unable to find either 

 description or figures of any such structure, I proceeded to 

 examine it further by means of dissection and serial sections. 



The position of the organ is shown in fig. 1. This is a 

 dissection of the posterior segments of a male cockroach 

 from which the tracheal system has been removed. In a 

 freshly-killed specimen it has a yellowish, transparent appear- 

 ance which renders it somewhat inconspicuous; but it was 

 present in every full-grown cockroach that I examined, both 

 male and female. In the male it measures about 2 mm. in 

 length, but in the female it is very much smaller, never 

 being more than about half the size of that of the male; 

 sections, however, show no histological difference. If the 

 nerve-cord is stretched to one side, the pouches, which before 

 appeared to be separate, are seen to be two lobes projecting 

 upwards and forwards from a median structure, which opens 

 below to the exterior by a single aperture on the ventral 

 surface of the animal between the sixth and seventh sternites. 

 This is clearly seen by a comparison of figs. 4 and 5, which 



