SKELETO-TROPIIIO TISSUES AND COXAL GLANDS. 131 



of London, where I have described and figured (witli the assis- 

 tance of my pupils, Mr. Benham and Miss Beck) tlie entire 

 muscular and skeletal system of Lirnulus and Scorpio. 



The observations recorded in the present memoir, in reference 

 to the structure of the coxal glands, Avill be found to have im- 

 portance, not only as adding one more to the many proofs of 

 the necessity for referring Lirnulus to the class Arachnida, but 

 also on account of the minute structure of the special cells of 

 the glands, which has a physiological significance. 



2. The Entosternites and massive connective tissue 

 OF LiMULUs, Scorpio, Mygale, and Apus. 



I have already figured in this Journal the entosternites of 

 Lirnulus and Mygale, and imperfectly that of Scorpio. I am 

 now able to submit to the reader more complete drawings^ of 

 that of Scorpio (PI. VI, figs. 5, 6, 7), and have introduced into 

 the same plate those of Lirnulus and Mygale for comparison. 



The entosternite of the Arachnida (including Limulus) is 

 essentially a plate of mat^sive skeletal tissue placed in the 

 median line of the prosoma, and provided with various paired 

 tendon-like outgrowths, to which muscles are attached connected 

 with the body wall and with the limbs. The plate itself is 

 moveable, having only delicate membranous connections of 

 skeletal tissue with the chitinous sclerites of the tegumentary 

 system, in addition to its muscular attachments. The bulk of 

 its substance is developed in a plane between the ventral nerve- 

 cords and the alimentary tract. lu Limulus and in Mygale the 

 entosternite does not embrace the alimentary canal nor the 

 nerve-cords in its substance, being simply continuous with the 

 delicate connective tissue which surrounds those organs ; 

 whereas in Scorpio the thickening and specialising of the con- 

 nective tissue extends from the main plate, so as to form a 

 subneural arch below the nerve-cords (PI. VI, fig. 6, snp.), thus 

 enclosing the nerve-cords in a neural canal (n c), whilst simi- 



' Eor these I am indebted to Miss Beck. They were prepared from dis- 

 sections of a number of specimens of Buthus cyaneus, of Ceylon. 



