38 S- <jOTo. 



on the inner surface of Avhieli some granuLitions are to be observed 

 (PL XIX, figs. 1 and 4). 



As to the cellular structure of this gland, which I believe is here 

 described for the (irst time in Calicot ijlc, there are, I think, two 

 alternative views to be considered. One would be to regard it as 

 being multicellular in its (jrigin and to have been formed by the in- 

 vagination of the epidermis; the other would be to regard it as 

 unicellular. Against the second view it may be urged that these 

 glands are too large to be regarded as unicellular — -inc(jmparably larger 

 than the luiicellular glands of similar function and position of the 

 Gijrodactijlidac — and that the presence of the internal cavity strongly 

 points to the other view ; while the similarity of its wall to that of the 

 similar glands of Diplozoon, Axine, and Diclidophora is also in favour of 

 the first view. 



Monocotyle — In this genus there are four pairs of sticky glands 

 at the anterior end of the body, and one in the posterior part. The 

 anterior glands are of exactly the same structure as those of Microcotijle, 

 and are arranged at e([ual distances along the front part of the 

 lateral border of the bod}^, on both sides of the anterior notch (PI. 

 X\U, %. 1). 



The posterior sticky ghuids are situated in that part of the body 

 which lies dorsally to the posterior sucker, and consist of numerous 

 small cells, each with a distinct, deeply stained nucleus and a very 

 finely granular or almost homogeneous cytoplasm which seems to be 

 destitute of an external membrane. The cells are of various sizes, 

 apparently owing to the different stages of secret(3ry activity ; and the 

 smaller ones are more deeply stained and have more finely granuku- 

 cytoplasm than the larger ones (PI. X^'II, figs. 5 and 12). In some 

 parts, these cells are so closely pressed against one another that their 

 boundaries become indistinct, and the whole appears somewdiat like a 



