204 



THE ORIGIN OF VERTEBRATES 



interrupted by two large, remarkable glandular structures. The 

 structure of these glands is better shown by means of sagittal sec- 

 tions. They are composed of very long, wedge-shaped cells, each of 

 which possesses a large, round nucleus at the basal end of the cell 

 (Pig. 87). These cells are arranged in bundles of about eight to ten, 

 which are separated from each other by connective tissue, the apex 

 of each conical bundle being directed into the cavity of the uterus ; 

 where this brush -like termination of the cells reaches the surface, the 

 chitinous layer is absent, so that this layer is, on surface view, seen 



Fig. 87. — Longitudinal Sec- 

 tion THROUGH THREE OF 



the Cones op the Uterine 

 Glands op the Scorpion. 





Fig. 88. — Sagittal Section through 

 the Uterine Gland of Scorpion, 

 showing the internal chitinous 

 Surface (b) and the Glandular 

 Cones (a) cut through at various 



DISTANCES FROM THE INTERNAL SUR- 

 FACE. 



(Fig. 88 (b)) to be pitted with round holes over that part of the 

 internal surface of the uterus where these glands are situated. Each 

 of these holes represents the termination of one of these cone-shaped 

 wedges of cells. If the section is cut across at right angles to the 

 axis of these cones, then its appearance is represented in Fig. 88 («), 

 and shows well the arrangement of the blocks of cells, separated from 

 each other by connective tissue. When the section passes through 

 the basal part of the cones, and only in that case, then the nuclei 

 of the cells appear, often in considerable numbers in one section, as 



