THE ANATOMY OF PENTASTOMUM TEEETIUSCULUM. 23 



usculum than in other forms yet described. They corre- 

 spond in position internally to the stigmata previously men- 

 tioned when dealing with the external anatomy. In the head 

 region they form an almost continuous layer beneath the 

 cuticle, longitudinal sections showing them lying closely side 

 by side. On the annuli they are confined to the anterior half 

 of each (fig. 29). 



Leuckart^ described in the young form of P. tsenioides, in 

 connection with the stigmata, small vesicle-like structures with 

 a definite wall, and containing fluid. In the older forms the 

 vesicle is replaced by a small process formed of a group of 

 cells which hangs down into the coelom. 



Hoyle, in P. protelis/ has described and figured them as 

 spheroidal in form, with their inner surfaces projecting but 

 little beyond that of the subcuticular epithelium. They take 

 up staining material easily, and each consists of from 6 to 9 

 cells. The outer aspect is moulded into a kind of short neck 

 which lies within the stigma, and is closed by a fine very darkly 

 stained line. 



Stiles^ describes and figures them in P. proboscideum as 

 small groups of clearly marked cells which lie immediately 

 within the stigma, not apparently arranged so as to form a 

 mass of definite shape. They are placed within a depression 

 on the inner side of the cuticle in such a way that their inner 

 ends do not reach to the level of those of the ordinary sub- 

 cuticular epithelium. 



In P. teretiusculum the stigmatic glands form a very 

 noticeable feature in all sections of the body-wall, and appear 

 to be more highly developed than in other forms. Each has 

 the definite shape represented in fig. 51, and consists of a 

 cluster of cells enclosed apparently in a common wall of con- 

 nective tissue. The whole is somewhat flask-shaped, with the 

 neck leading into the stigma {St. Gl. 0.). The individual cells 

 can in good sections be distinguished, and then, as shown 



1 Loc. cit„ p. 33, Taf. i, fig. 7, and Taf. iii, figs. 18—21. 



2 Loc. cit., p. 180, pi, xxvii, figs. 9 and 11. 

 5 Loc. cit,, p, 119, Taf. viii, fig. 49. 



