THE EVIDENCE OF THE THYROID GLAXD 



205 



is seen in Yv* 89. In Fig. 88 the section shows at b the holes in 

 the chitin in which the cones terminate, and then a series of layers 

 of sections through the cones further and 

 further away from their apices. 



These conical groups of long cells, repre- 

 sented in Fig. 87, form on each side of the 

 uterus a gland, which is continuous along 

 its whole length, and thus forms a line 

 of secreting surface on each side, just as 

 in the corresponding arrangement of the 

 glandular structures in the thyroid of Am- 

 moccetes. This uterus and glandular ar- 

 rangement is found in both sexes ; the gland is, however, more 

 developed in the male than in the female scorpion. 



The resemblance between the structure of the thyroid of Ammo- 

 ccetes and the uterus of the scorpion is most striking, except in two 

 respects, viz. the nature of the lining of the non-glandular part of 

 the cavity — in the one case ciliated, in the other chitinous — and the 

 place of exit of the cavity, the thyroid of Ammoccetes opening into 



Fig. 89. — Transverse Sec- 

 tion THROUGH THE BASAL 



Part of the Uterine 

 Glands op the Scorpion. 



AMMOCCETES. 



SCORPION. 



Muco-cartilage Operculum 



Branchial cartilage 

 Fig. 90.— Section op Central Chamber op Thyroid op Ammoccetes and Section 



of Uterus of Scorpion. 



the respiratory chamber, while the uterus of Scorpio opens direct to 

 the exterior. 



With respect to the first difference, the same difficulty is met 



