NEW ORGAN IN PBRIPLANETA ORIBNTALIS. 381 



and in each a denser patch of granules surrounds a stout tube 

 which extends from the region of the nucleus to the inner 

 edge of the cell. Attached to the lining membrane, some- 

 times singly, sometimes in groups, are immensely long hairs 

 with free extremities, directed towards the epithelial layer. 

 The cells of this outer layer appear to migrate inwards, and 

 there degenerate, leaving only irregular nuclei very unlike 

 the large round nuclei of the granular cells. In a young 

 specimen the epithelial cells are not granular, and there is 

 no intermediate tissue between them and the chitinous lining-. 

 This suggests that the granules represent the secretion of 

 the gland, and their absence in the young indicates that the 

 organ is immature. 



This work has been carried on in the Department of Com- 

 parative Anatomy in the Oxford University Museum, and I 

 wish to express my warm thanks to Mr. Groodrich for much 

 kind help throughout the course of my research. 



Eeferences. 

 Claus.— ' Zeit. f. wiss. Zool.,' Bd. xi, 1861. 

 Kraase.— ' Zool. Anz./ Bd. xiii, 1890. 

 MiNCHiN. — ' Quart. Journ. Micr. Sci.,' vol. xxix, 1888. 



EXPLANATION OF PLATE 15, 



Illustrating Miss Ruth M. Harrison's paper, " Preliminary 

 Account of a New Organ in Periplaneta oriental is." 



List of Reference Letters. 



G. The gland, c. Cerca. epi. Epithelium of body wall, epi.g. Epithe- 

 lium of gland, f. b. Fat body. gr. c. Granular cells, h. Hairs. /. Lumen 

 of gland, l.m. Lining membrane. »/._^/. Mushroom-shaped gland. «. Nuclei 

 of disintegrating cells, r. Rectum. *. Style, th.r.c. Thickened rim of 

 chitin on sternite 7 round the external aperture, ir. v. Tracheal vessel, (u. 

 Tubes in the granular cells, hth abd. g. and ^th abcl. g. Fifth and sixth abdo- 

 VOL. 50, PART 2. — NEW SERIES. 27 



