-46- 



The lateral invagination deeply indents each of the halves into 

 which the gland is divided by the median lamella. (Mag, 240 

 diam. ) 



Fig. 5 f. Transverse section posterior to Fig. 5 e . 

 The ciliated grooves are nearly joined, the ciliated layer of 

 cells is now distinct, as are two of the four cell-groups. The 

 lateral invagination is very deep. (Mag. 240 diam. ) 



Fi g. 5 g. Transverse section posterior to Fig, 5 f but 

 still anterior to the duct. The ciliated grooves have united 

 to form a single deep groove which is here spread out at the 

 bottom, giving it the shape, in cross section, of an inverted 

 letter T. The structure of the gland is now about the same as 

 in the preceding section. (Iii^ag. 240 diam.) 



Fig. 5 h . Transverse section posterior to Fjg, 5 g and 

 just anterior to the opening of the duct. The structure of the 

 gland is the same as in Fig. 5 g but the shape of the ciliated 

 groove has changed somewhat. (Mag. 240 diam.) 



Fig. 5 i. Transverse section through the opening of 

 the duct into the ciliated groove. Shows that the median cili- 

 ated chamber opens directly into the deep ciliated groove, 

 while the lateral ciliated chambers open into the ciliated groove 

 through the side pouches noticed in the last two preceding fig- 

 ures. The lateral invaginations, from this point to the poste- 

 rior end, divide the gland into three distinct parts, a median 



