380 RUTH M. HARRTSOX. 



migrate inwards and disintegrate ; the animal from which 

 this gland was taken was a fine large male, and the scarcity 

 of grannlar cells may possibly be explained by the fact that 

 the organ is ceasing to be functional, and is in a degenerate 

 condition. The nature of the secretion and the function of 

 the whole organ I have not so far investigated ; but this I 

 hope to do, together with a further study of the individual 

 elements and their relations to each other. 



The curious tubes in the outer granular layer bear a strong 

 resemblance to certain tubes described and figured by Claus 

 in a stink-gland of the larva of the Coleopteron Chrysomela. 

 But the hairs are quite unlike those described by Minchin in 

 the dorsal glands of this same species of Periplaneta, or 

 those described by Kraase in a dorsal stink-gland of the Blattid 

 Aphlebia, in that they project inwards, away from the lumen 

 of the gland. Whether there is any definite relation between 

 these tubes and the bunches of hairs I have not been able to 

 ascertain. The tubes seem to come to an abrupt end near 

 the nucleus, and I cannot trace them beyond the limit of the 

 granular cells; the hairs are comparatively stout and 

 cylindrical at their bases, but appear gradually to taper 

 away at their free extremities. But it seems doubtful 

 that this should actually be the case ; for the chitinous 

 lining membrane is quite continuous, and it is difficult to 

 see how the secretion reaches the exterior unless these hairs 

 serve in some way as a means of communication between the 

 lumen of the gland and the secreting cells. 



In the above description it has been shown that Peri- 

 planeta oriental is possesses a glandular organ on its 

 ventral side, lying in the sixth abdominal segment, between 

 the fifth and sixth abdominal ganglia, and opening to the 

 exterior between the sixth and seventh stcrnites. 'J'his 

 opening is median, and from it the gland extends upwards 

 and forwards as two distinct lobes. It is composed of a 

 layer of modified epithelial cells lined by a chitinous mem- 

 brane continuous with the external chitinous skeleton of the 

 insect. The epithelial cells of the adult arc finely granular. 



