158 PROFESSOR E. RAY LANKESTER. 



filled by the remarkable colloid homogeneous substance which I 

 have mentioned above as occurring in certain fissures in the 

 entosternite of that animal. Small nuclei which stain pink 

 with carmine, and are surrounded by a delicate envelope of 

 unstained protoplasm are scattered in isolated positions 

 throughout this colloid matrix. The tissue so constituted I 

 have termed above, colloid tissue. (PI. XII, fig. 1, col.) 

 There is thus then in Mygale no space which could serve as a 

 blood- carrying space between the cseca of the gland. 



The cseca of the gland are larger than in Scorpio, they have 

 an irregular outline and are often greatly compressed, that is, 

 have a long, narrow and irregular lumen. The cells which 

 line these cseca are of great size, very much larger than the 

 corresponding cells in Scorpio. The measurements are given 

 on Plate XII. Just as in Scorpio so here we find a strongly 

 refringent, dense, cortical substance developed on the deep 

 surface of the gland cells (PI. XII, fig. 1, cr.) where they 

 rest on the colloid tissue. The protoplasm is soft and delicate 

 and easily tears away from this dense cortical layer. The 

 gigantic nuclei are frequently to be seen in sections lying 

 loose in a coagulum in the lumen of the glandular cseca. 



12. Structure of the coxal glands of Limulus. 



At first sight the coxal glands of Limulus do not seem to be 

 constructed on the same type as those of Scorpio and Mygale. 

 A great difference in appearance is brought about by the fact 

 that in Limulus the intercsecal connective tissue is very 

 abundant, and forms the bulk of the gland (PI. XII, fig. 4 ; 

 a, b, e), whilst the cells which constitute the layer lining the 

 glandular cseca are not large cells, but have nuclei of the 

 same size as those of the intercsecal connective tissue, and no 

 excess of protoplasm. Accordingly the observer does not 

 readily draw a distinction between the gland epithelium and 

 the surrounding connective tissue. Indeed, to distinguish 

 between them is often very difficult, for the intercsecal con- 

 nective tissue presents numerous lacunse (which resemble those 

 of the usual lacunar tissue), and are set round with cells in the 



