waite: antennal glands in homarus americanus. 1G5 



runs obliquely ventrad and laterad. It is short, and soon branches to 

 become continuous with the lumina of the various labyrinth tubules. 



At the border of this short channel, as indicated at a in Figure 2, 

 there is a sudden transition from tbe cells of the endsac to those of the 

 labyrinth, there being no cells of intermediate character. The boundary 

 of this opening is the only place where the cells of endsac and labyrinth 

 come into contact. At all other places where endsac and labyrinth come 

 together, the basement membranes of the two are face to face. 



The labyrinth is not a single pocket with evaginations like the endsac, 

 but is composed of a system of branching tubules ; these are not, how- 

 ever, simply coiled tubules, for they undergo anastomosis at frequent 

 intervals, and it is therefore impossible to trace any single tubule for a 

 great distance. Moreover, the tubules are not of uniform calibre, but 

 have numerous outpocketings, which still further complicate the appear- 

 ances presented in sections. This communicating system of lumina is so 

 complicated that it is impossible to say that it presents a definite plan. 

 It is certain, however, that it does not represent one or a few coiled tu- 

 bules, as has been described for Astacus. The whole system of laby- 

 rinthine passages is lined by a continuous layer of epithelium. The 

 basement membrane (Figs. 7 and 8, mb. ba.) of this epithelium is 

 somewhat thicker than that of the epithelium of the endsac. The spaces 

 between the epithelial lining of adjacent tubules is occupied by a vascu- 

 lar connective tissue (Fig. 7, tis. con't.), like that described in the septa 

 of the endsac (p. 163). The blood-vessels and lacunae found in this tissue 

 contain blood corpuscles (Fig. 8, vas. sng.). 



The epithelial cells in different regions of the labyrinth do not show 

 differences of form, but they are very unlike those of the endsac. The 

 cytoplasm is denser and stains more deeply, and the vacuolated condition 

 so characteristic of the cells of the endsac is not seen. Instead, the 

 cytoplasm contains large numbers of granules of very uniform size and 

 power of refraction, and exhibits a striation which is perpendicular to 

 the basement membrane. The oval nuclei lie near the middle of the 

 cell, and are somewhat larger than those of the epithelium of the endsac. 

 But the distinguishing feature of the epithelium of the labyrinth is its 

 free border. This differs in different glands, and in different parts of the 

 same gland ; the extreme conditions may, indeed, be seen even in neigh- 

 boring regions of the same tubule. In Figures 7 and 8 are shown the 

 extremes of the conditions seen. The free border of the cells shown in 

 Figure 8 appears striate, and there is formed a layer which, though it is 

 not a true cuticula, resembles one. The parallel striae represent partitions 

 vol. xxxv. — no. 7. 2 



